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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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![Linus Torvalds](/assets/img/avatar_default.png)
switching from a user process to a kernel thread. - More folio conversions from Kefeng Wang, Zhang Peng and Pankaj Raghav. - zsmalloc performance improvements from Sergey Senozhatsky. - Yue Zhao has found and fixed some data race issues around the alteration of memcg userspace tunables. - VFS rationalizations from Christoph Hellwig: - removal of most of the callers of write_one_page(). - make __filemap_get_folio()'s return value more useful - Luis Chamberlain has changed tmpfs so it no longer requires swap backing. Use `mount -o noswap'. - Qi Zheng has made the slab shrinkers operate locklessly, providing some scalability benefits. - Keith Busch has improved dmapool's performance, making part of its operations O(1) rather than O(n). - Peter Xu adds the UFFD_FEATURE_WP_UNPOPULATED feature to userfaultd, permitting userspace to wr-protect anon memory unpopulated ptes. - Kirill Shutemov has changed MAX_ORDER's meaning to be inclusive rather than exclusive, and has fixed a bunch of errors which were caused by its unintuitive meaning. - Axel Rasmussen give userfaultfd the UFFDIO_CONTINUE_MODE_WP feature, which causes minor faults to install a write-protected pte. - Vlastimil Babka has done some maintenance work on vma_merge(): cleanups to the kernel code and improvements to our userspace test harness. - Cleanups to do_fault_around() by Lorenzo Stoakes. - Mike Rapoport has moved a lot of initialization code out of various mm/ files and into mm/mm_init.c. - Lorenzo Stoakes removd vmf_insert_mixed_prot(), which was added for DRM, but DRM doesn't use it any more. - Lorenzo has also coverted read_kcore() and vread() to use iterators and has thereby removed the use of bounce buffers in some cases. - Lorenzo has also contributed further cleanups of vma_merge(). - Chaitanya Prakash provides some fixes to the mmap selftesting code. - Matthew Wilcox changes xfs and afs so they no longer take sleeping locks in ->map_page(), a step towards RCUification of pagefaults. - Suren Baghdasaryan has improved mmap_lock scalability by switching to per-VMA locking. - Frederic Weisbecker has reworked the percpu cache draining so that it no longer causes latency glitches on cpu isolated workloads. - Mike Rapoport cleans up and corrects the ARCH_FORCE_MAX_ORDER Kconfig logic. - Liu Shixin has changed zswap's initialization so we no longer waste a chunk of memory if zswap is not being used. - Yosry Ahmed has improved the performance of memcg statistics flushing. - David Stevens has fixed several issues involving khugepaged, userfaultfd and shmem. - Christoph Hellwig has provided some cleanup work to zram's IO-related code paths. - David Hildenbrand has fixed up some issues in the selftest code's testing of our pte state changing. - Pankaj Raghav has made page_endio() unneeded and has removed it. - Peter Xu contributed some rationalizations of the userfaultfd selftests. - Yosry Ahmed has fixed an issue around memcg's page recalim accounting. - Chaitanya Prakash has fixed some arm-related issues in the selftests/mm code. - Longlong Xia has improved the way in which KSM handles hwpoisoned pages. - Peter Xu fixes a few issues with uffd-wp at fork() time. - Stefan Roesch has changed KSM so that it may now be used on a per-process and per-cgroup basis. -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQTTMBEPP41GrTpTJgfdBJ7gKXxAjgUCZEr3zQAKCRDdBJ7gKXxA jlLoAP0fpQBipwFxED0Us4SKQfupV6z4caXNJGPeay7Aj11/kQD/aMRC2uPfgr96 eMG3kwn2pqkB9ST2QpkaRbxA//eMbQY= =J+Dj -----END PGP SIGNATURE----- Merge tag 'mm-stable-2023-04-27-15-30' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Pull MM updates from Andrew Morton: - Nick Piggin's "shoot lazy tlbs" series, to improve the peformance of switching from a user process to a kernel thread. - More folio conversions from Kefeng Wang, Zhang Peng and Pankaj Raghav. - zsmalloc performance improvements from Sergey Senozhatsky. - Yue Zhao has found and fixed some data race issues around the alteration of memcg userspace tunables. - VFS rationalizations from Christoph Hellwig: - removal of most of the callers of write_one_page() - make __filemap_get_folio()'s return value more useful - Luis Chamberlain has changed tmpfs so it no longer requires swap backing. Use `mount -o noswap'. - Qi Zheng has made the slab shrinkers operate locklessly, providing some scalability benefits. - Keith Busch has improved dmapool's performance, making part of its operations O(1) rather than O(n). - Peter Xu adds the UFFD_FEATURE_WP_UNPOPULATED feature to userfaultd, permitting userspace to wr-protect anon memory unpopulated ptes. - Kirill Shutemov has changed MAX_ORDER's meaning to be inclusive rather than exclusive, and has fixed a bunch of errors which were caused by its unintuitive meaning. - Axel Rasmussen give userfaultfd the UFFDIO_CONTINUE_MODE_WP feature, which causes minor faults to install a write-protected pte. - Vlastimil Babka has done some maintenance work on vma_merge(): cleanups to the kernel code and improvements to our userspace test harness. - Cleanups to do_fault_around() by Lorenzo Stoakes. - Mike Rapoport has moved a lot of initialization code out of various mm/ files and into mm/mm_init.c. - Lorenzo Stoakes removd vmf_insert_mixed_prot(), which was added for DRM, but DRM doesn't use it any more. - Lorenzo has also coverted read_kcore() and vread() to use iterators and has thereby removed the use of bounce buffers in some cases. - Lorenzo has also contributed further cleanups of vma_merge(). - Chaitanya Prakash provides some fixes to the mmap selftesting code. - Matthew Wilcox changes xfs and afs so they no longer take sleeping locks in ->map_page(), a step towards RCUification of pagefaults. - Suren Baghdasaryan has improved mmap_lock scalability by switching to per-VMA locking. - Frederic Weisbecker has reworked the percpu cache draining so that it no longer causes latency glitches on cpu isolated workloads. - Mike Rapoport cleans up and corrects the ARCH_FORCE_MAX_ORDER Kconfig logic. - Liu Shixin has changed zswap's initialization so we no longer waste a chunk of memory if zswap is not being used. - Yosry Ahmed has improved the performance of memcg statistics flushing. - David Stevens has fixed several issues involving khugepaged, userfaultfd and shmem. - Christoph Hellwig has provided some cleanup work to zram's IO-related code paths. - David Hildenbrand has fixed up some issues in the selftest code's testing of our pte state changing. - Pankaj Raghav has made page_endio() unneeded and has removed it. - Peter Xu contributed some rationalizations of the userfaultfd selftests. - Yosry Ahmed has fixed an issue around memcg's page recalim accounting. - Chaitanya Prakash has fixed some arm-related issues in the selftests/mm code. - Longlong Xia has improved the way in which KSM handles hwpoisoned pages. - Peter Xu fixes a few issues with uffd-wp at fork() time. - Stefan Roesch has changed KSM so that it may now be used on a per-process and per-cgroup basis. * tag 'mm-stable-2023-04-27-15-30' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (369 commits) mm,unmap: avoid flushing TLB in batch if PTE is inaccessible shmem: restrict noswap option to initial user namespace mm/khugepaged: fix conflicting mods to collapse_file() sparse: remove unnecessary 0 values from rc mm: move 'mmap_min_addr' logic from callers into vm_unmapped_area() hugetlb: pte_alloc_huge() to replace huge pte_alloc_map() maple_tree: fix allocation in mas_sparse_area() mm: do not increment pgfault stats when page fault handler retries zsmalloc: allow only one active pool compaction context selftests/mm: add new selftests for KSM mm: add new KSM process and sysfs knobs mm: add new api to enable ksm per process mm: shrinkers: fix debugfs file permissions mm: don't check VMA write permissions if the PTE/PMD indicates write permissions migrate_pages_batch: fix statistics for longterm pin retry userfaultfd: use helper function range_in_vma() lib/show_mem.c: use for_each_populated_zone() simplify code mm: correct arg in reclaim_pages()/reclaim_clean_pages_from_list() fs/buffer: convert create_page_buffers to folio_create_buffers fs/buffer: add folio_create_empty_buffers helper ...
1182 lines
35 KiB
C
1182 lines
35 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* KFENCE guarded object allocator and fault handling.
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*
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* Copyright (C) 2020, Google LLC.
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*/
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#define pr_fmt(fmt) "kfence: " fmt
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#include <linux/atomic.h>
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#include <linux/bug.h>
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#include <linux/debugfs.h>
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#include <linux/hash.h>
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#include <linux/irq_work.h>
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#include <linux/jhash.h>
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#include <linux/kcsan-checks.h>
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#include <linux/kfence.h>
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#include <linux/kmemleak.h>
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#include <linux/list.h>
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#include <linux/lockdep.h>
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#include <linux/log2.h>
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#include <linux/memblock.h>
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#include <linux/moduleparam.h>
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#include <linux/notifier.h>
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#include <linux/panic_notifier.h>
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#include <linux/random.h>
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#include <linux/rcupdate.h>
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#include <linux/sched/clock.h>
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#include <linux/seq_file.h>
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#include <linux/slab.h>
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#include <linux/spinlock.h>
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#include <linux/string.h>
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#include <asm/kfence.h>
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#include "kfence.h"
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/* Disables KFENCE on the first warning assuming an irrecoverable error. */
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#define KFENCE_WARN_ON(cond) \
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({ \
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const bool __cond = WARN_ON(cond); \
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if (unlikely(__cond)) { \
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WRITE_ONCE(kfence_enabled, false); \
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disabled_by_warn = true; \
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} \
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__cond; \
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})
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/* === Data ================================================================= */
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static bool kfence_enabled __read_mostly;
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static bool disabled_by_warn __read_mostly;
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unsigned long kfence_sample_interval __read_mostly = CONFIG_KFENCE_SAMPLE_INTERVAL;
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EXPORT_SYMBOL_GPL(kfence_sample_interval); /* Export for test modules. */
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#ifdef MODULE_PARAM_PREFIX
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#undef MODULE_PARAM_PREFIX
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#endif
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#define MODULE_PARAM_PREFIX "kfence."
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static int kfence_enable_late(void);
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static int param_set_sample_interval(const char *val, const struct kernel_param *kp)
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{
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unsigned long num;
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int ret = kstrtoul(val, 0, &num);
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if (ret < 0)
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return ret;
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/* Using 0 to indicate KFENCE is disabled. */
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if (!num && READ_ONCE(kfence_enabled)) {
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pr_info("disabled\n");
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WRITE_ONCE(kfence_enabled, false);
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}
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*((unsigned long *)kp->arg) = num;
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if (num && !READ_ONCE(kfence_enabled) && system_state != SYSTEM_BOOTING)
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return disabled_by_warn ? -EINVAL : kfence_enable_late();
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return 0;
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}
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static int param_get_sample_interval(char *buffer, const struct kernel_param *kp)
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{
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if (!READ_ONCE(kfence_enabled))
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return sprintf(buffer, "0\n");
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return param_get_ulong(buffer, kp);
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}
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static const struct kernel_param_ops sample_interval_param_ops = {
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.set = param_set_sample_interval,
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.get = param_get_sample_interval,
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};
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module_param_cb(sample_interval, &sample_interval_param_ops, &kfence_sample_interval, 0600);
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/* Pool usage% threshold when currently covered allocations are skipped. */
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static unsigned long kfence_skip_covered_thresh __read_mostly = 75;
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module_param_named(skip_covered_thresh, kfence_skip_covered_thresh, ulong, 0644);
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/* If true, use a deferrable timer. */
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static bool kfence_deferrable __read_mostly = IS_ENABLED(CONFIG_KFENCE_DEFERRABLE);
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module_param_named(deferrable, kfence_deferrable, bool, 0444);
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/* If true, check all canary bytes on panic. */
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static bool kfence_check_on_panic __read_mostly;
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module_param_named(check_on_panic, kfence_check_on_panic, bool, 0444);
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/* The pool of pages used for guard pages and objects. */
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char *__kfence_pool __read_mostly;
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EXPORT_SYMBOL(__kfence_pool); /* Export for test modules. */
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/*
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* Per-object metadata, with one-to-one mapping of object metadata to
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* backing pages (in __kfence_pool).
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*/
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static_assert(CONFIG_KFENCE_NUM_OBJECTS > 0);
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struct kfence_metadata kfence_metadata[CONFIG_KFENCE_NUM_OBJECTS];
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/* Freelist with available objects. */
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static struct list_head kfence_freelist = LIST_HEAD_INIT(kfence_freelist);
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static DEFINE_RAW_SPINLOCK(kfence_freelist_lock); /* Lock protecting freelist. */
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/*
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* The static key to set up a KFENCE allocation; or if static keys are not used
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* to gate allocations, to avoid a load and compare if KFENCE is disabled.
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*/
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DEFINE_STATIC_KEY_FALSE(kfence_allocation_key);
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/* Gates the allocation, ensuring only one succeeds in a given period. */
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atomic_t kfence_allocation_gate = ATOMIC_INIT(1);
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/*
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* A Counting Bloom filter of allocation coverage: limits currently covered
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* allocations of the same source filling up the pool.
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*
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* Assuming a range of 15%-85% unique allocations in the pool at any point in
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* time, the below parameters provide a probablity of 0.02-0.33 for false
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* positive hits respectively:
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*
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* P(alloc_traces) = (1 - e^(-HNUM * (alloc_traces / SIZE)) ^ HNUM
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*/
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#define ALLOC_COVERED_HNUM 2
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#define ALLOC_COVERED_ORDER (const_ilog2(CONFIG_KFENCE_NUM_OBJECTS) + 2)
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#define ALLOC_COVERED_SIZE (1 << ALLOC_COVERED_ORDER)
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#define ALLOC_COVERED_HNEXT(h) hash_32(h, ALLOC_COVERED_ORDER)
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#define ALLOC_COVERED_MASK (ALLOC_COVERED_SIZE - 1)
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static atomic_t alloc_covered[ALLOC_COVERED_SIZE];
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/* Stack depth used to determine uniqueness of an allocation. */
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#define UNIQUE_ALLOC_STACK_DEPTH ((size_t)8)
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/*
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* Randomness for stack hashes, making the same collisions across reboots and
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* different machines less likely.
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*/
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static u32 stack_hash_seed __ro_after_init;
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/* Statistics counters for debugfs. */
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enum kfence_counter_id {
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KFENCE_COUNTER_ALLOCATED,
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KFENCE_COUNTER_ALLOCS,
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KFENCE_COUNTER_FREES,
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KFENCE_COUNTER_ZOMBIES,
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KFENCE_COUNTER_BUGS,
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KFENCE_COUNTER_SKIP_INCOMPAT,
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KFENCE_COUNTER_SKIP_CAPACITY,
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KFENCE_COUNTER_SKIP_COVERED,
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KFENCE_COUNTER_COUNT,
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};
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static atomic_long_t counters[KFENCE_COUNTER_COUNT];
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static const char *const counter_names[] = {
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[KFENCE_COUNTER_ALLOCATED] = "currently allocated",
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[KFENCE_COUNTER_ALLOCS] = "total allocations",
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[KFENCE_COUNTER_FREES] = "total frees",
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[KFENCE_COUNTER_ZOMBIES] = "zombie allocations",
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[KFENCE_COUNTER_BUGS] = "total bugs",
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[KFENCE_COUNTER_SKIP_INCOMPAT] = "skipped allocations (incompatible)",
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[KFENCE_COUNTER_SKIP_CAPACITY] = "skipped allocations (capacity)",
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[KFENCE_COUNTER_SKIP_COVERED] = "skipped allocations (covered)",
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};
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static_assert(ARRAY_SIZE(counter_names) == KFENCE_COUNTER_COUNT);
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/* === Internals ============================================================ */
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static inline bool should_skip_covered(void)
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{
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unsigned long thresh = (CONFIG_KFENCE_NUM_OBJECTS * kfence_skip_covered_thresh) / 100;
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return atomic_long_read(&counters[KFENCE_COUNTER_ALLOCATED]) > thresh;
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}
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static u32 get_alloc_stack_hash(unsigned long *stack_entries, size_t num_entries)
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{
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num_entries = min(num_entries, UNIQUE_ALLOC_STACK_DEPTH);
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num_entries = filter_irq_stacks(stack_entries, num_entries);
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return jhash(stack_entries, num_entries * sizeof(stack_entries[0]), stack_hash_seed);
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}
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/*
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* Adds (or subtracts) count @val for allocation stack trace hash
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* @alloc_stack_hash from Counting Bloom filter.
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*/
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static void alloc_covered_add(u32 alloc_stack_hash, int val)
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{
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int i;
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for (i = 0; i < ALLOC_COVERED_HNUM; i++) {
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atomic_add(val, &alloc_covered[alloc_stack_hash & ALLOC_COVERED_MASK]);
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alloc_stack_hash = ALLOC_COVERED_HNEXT(alloc_stack_hash);
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}
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}
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/*
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* Returns true if the allocation stack trace hash @alloc_stack_hash is
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* currently contained (non-zero count) in Counting Bloom filter.
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*/
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static bool alloc_covered_contains(u32 alloc_stack_hash)
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{
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int i;
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for (i = 0; i < ALLOC_COVERED_HNUM; i++) {
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if (!atomic_read(&alloc_covered[alloc_stack_hash & ALLOC_COVERED_MASK]))
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return false;
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alloc_stack_hash = ALLOC_COVERED_HNEXT(alloc_stack_hash);
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}
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return true;
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}
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static bool kfence_protect(unsigned long addr)
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{
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return !KFENCE_WARN_ON(!kfence_protect_page(ALIGN_DOWN(addr, PAGE_SIZE), true));
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}
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static bool kfence_unprotect(unsigned long addr)
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{
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return !KFENCE_WARN_ON(!kfence_protect_page(ALIGN_DOWN(addr, PAGE_SIZE), false));
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}
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static inline unsigned long metadata_to_pageaddr(const struct kfence_metadata *meta)
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{
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unsigned long offset = (meta - kfence_metadata + 1) * PAGE_SIZE * 2;
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unsigned long pageaddr = (unsigned long)&__kfence_pool[offset];
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/* The checks do not affect performance; only called from slow-paths. */
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/* Only call with a pointer into kfence_metadata. */
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if (KFENCE_WARN_ON(meta < kfence_metadata ||
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meta >= kfence_metadata + CONFIG_KFENCE_NUM_OBJECTS))
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return 0;
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/*
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* This metadata object only ever maps to 1 page; verify that the stored
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* address is in the expected range.
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*/
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if (KFENCE_WARN_ON(ALIGN_DOWN(meta->addr, PAGE_SIZE) != pageaddr))
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return 0;
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return pageaddr;
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}
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/*
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* Update the object's metadata state, including updating the alloc/free stacks
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* depending on the state transition.
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*/
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static noinline void
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metadata_update_state(struct kfence_metadata *meta, enum kfence_object_state next,
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unsigned long *stack_entries, size_t num_stack_entries)
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{
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struct kfence_track *track =
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next == KFENCE_OBJECT_FREED ? &meta->free_track : &meta->alloc_track;
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lockdep_assert_held(&meta->lock);
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if (stack_entries) {
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memcpy(track->stack_entries, stack_entries,
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num_stack_entries * sizeof(stack_entries[0]));
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} else {
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/*
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* Skip over 1 (this) functions; noinline ensures we do not
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* accidentally skip over the caller by never inlining.
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*/
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num_stack_entries = stack_trace_save(track->stack_entries, KFENCE_STACK_DEPTH, 1);
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}
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track->num_stack_entries = num_stack_entries;
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track->pid = task_pid_nr(current);
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track->cpu = raw_smp_processor_id();
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track->ts_nsec = local_clock(); /* Same source as printk timestamps. */
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/*
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* Pairs with READ_ONCE() in
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* kfence_shutdown_cache(),
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* kfence_handle_page_fault().
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*/
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WRITE_ONCE(meta->state, next);
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}
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/* Check canary byte at @addr. */
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static inline bool check_canary_byte(u8 *addr)
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{
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struct kfence_metadata *meta;
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unsigned long flags;
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if (likely(*addr == KFENCE_CANARY_PATTERN_U8(addr)))
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return true;
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atomic_long_inc(&counters[KFENCE_COUNTER_BUGS]);
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meta = addr_to_metadata((unsigned long)addr);
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raw_spin_lock_irqsave(&meta->lock, flags);
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kfence_report_error((unsigned long)addr, false, NULL, meta, KFENCE_ERROR_CORRUPTION);
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raw_spin_unlock_irqrestore(&meta->lock, flags);
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return false;
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}
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static inline void set_canary(const struct kfence_metadata *meta)
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{
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const unsigned long pageaddr = ALIGN_DOWN(meta->addr, PAGE_SIZE);
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unsigned long addr = pageaddr;
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/*
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* The canary may be written to part of the object memory, but it does
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* not affect it. The user should initialize the object before using it.
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*/
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for (; addr < meta->addr; addr += sizeof(u64))
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*((u64 *)addr) = KFENCE_CANARY_PATTERN_U64;
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addr = ALIGN_DOWN(meta->addr + meta->size, sizeof(u64));
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for (; addr - pageaddr < PAGE_SIZE; addr += sizeof(u64))
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*((u64 *)addr) = KFENCE_CANARY_PATTERN_U64;
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}
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static inline void check_canary(const struct kfence_metadata *meta)
|
|
{
|
|
const unsigned long pageaddr = ALIGN_DOWN(meta->addr, PAGE_SIZE);
|
|
unsigned long addr = pageaddr;
|
|
|
|
/*
|
|
* We'll iterate over each canary byte per-side until a corrupted byte
|
|
* is found. However, we'll still iterate over the canary bytes to the
|
|
* right of the object even if there was an error in the canary bytes to
|
|
* the left of the object. Specifically, if check_canary_byte()
|
|
* generates an error, showing both sides might give more clues as to
|
|
* what the error is about when displaying which bytes were corrupted.
|
|
*/
|
|
|
|
/* Apply to left of object. */
|
|
for (; meta->addr - addr >= sizeof(u64); addr += sizeof(u64)) {
|
|
if (unlikely(*((u64 *)addr) != KFENCE_CANARY_PATTERN_U64))
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* If the canary is corrupted in a certain 64 bytes, or the canary
|
|
* memory cannot be completely covered by multiple consecutive 64 bytes,
|
|
* it needs to be checked one by one.
|
|
*/
|
|
for (; addr < meta->addr; addr++) {
|
|
if (unlikely(!check_canary_byte((u8 *)addr)))
|
|
break;
|
|
}
|
|
|
|
/* Apply to right of object. */
|
|
for (addr = meta->addr + meta->size; addr % sizeof(u64) != 0; addr++) {
|
|
if (unlikely(!check_canary_byte((u8 *)addr)))
|
|
return;
|
|
}
|
|
for (; addr - pageaddr < PAGE_SIZE; addr += sizeof(u64)) {
|
|
if (unlikely(*((u64 *)addr) != KFENCE_CANARY_PATTERN_U64)) {
|
|
|
|
for (; addr - pageaddr < PAGE_SIZE; addr++) {
|
|
if (!check_canary_byte((u8 *)addr))
|
|
return;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
static void *kfence_guarded_alloc(struct kmem_cache *cache, size_t size, gfp_t gfp,
|
|
unsigned long *stack_entries, size_t num_stack_entries,
|
|
u32 alloc_stack_hash)
|
|
{
|
|
struct kfence_metadata *meta = NULL;
|
|
unsigned long flags;
|
|
struct slab *slab;
|
|
void *addr;
|
|
const bool random_right_allocate = get_random_u32_below(2);
|
|
const bool random_fault = CONFIG_KFENCE_STRESS_TEST_FAULTS &&
|
|
!get_random_u32_below(CONFIG_KFENCE_STRESS_TEST_FAULTS);
|
|
|
|
/* Try to obtain a free object. */
|
|
raw_spin_lock_irqsave(&kfence_freelist_lock, flags);
|
|
if (!list_empty(&kfence_freelist)) {
|
|
meta = list_entry(kfence_freelist.next, struct kfence_metadata, list);
|
|
list_del_init(&meta->list);
|
|
}
|
|
raw_spin_unlock_irqrestore(&kfence_freelist_lock, flags);
|
|
if (!meta) {
|
|
atomic_long_inc(&counters[KFENCE_COUNTER_SKIP_CAPACITY]);
|
|
return NULL;
|
|
}
|
|
|
|
if (unlikely(!raw_spin_trylock_irqsave(&meta->lock, flags))) {
|
|
/*
|
|
* This is extremely unlikely -- we are reporting on a
|
|
* use-after-free, which locked meta->lock, and the reporting
|
|
* code via printk calls kmalloc() which ends up in
|
|
* kfence_alloc() and tries to grab the same object that we're
|
|
* reporting on. While it has never been observed, lockdep does
|
|
* report that there is a possibility of deadlock. Fix it by
|
|
* using trylock and bailing out gracefully.
|
|
*/
|
|
raw_spin_lock_irqsave(&kfence_freelist_lock, flags);
|
|
/* Put the object back on the freelist. */
|
|
list_add_tail(&meta->list, &kfence_freelist);
|
|
raw_spin_unlock_irqrestore(&kfence_freelist_lock, flags);
|
|
|
|
return NULL;
|
|
}
|
|
|
|
meta->addr = metadata_to_pageaddr(meta);
|
|
/* Unprotect if we're reusing this page. */
|
|
if (meta->state == KFENCE_OBJECT_FREED)
|
|
kfence_unprotect(meta->addr);
|
|
|
|
/*
|
|
* Note: for allocations made before RNG initialization, will always
|
|
* return zero. We still benefit from enabling KFENCE as early as
|
|
* possible, even when the RNG is not yet available, as this will allow
|
|
* KFENCE to detect bugs due to earlier allocations. The only downside
|
|
* is that the out-of-bounds accesses detected are deterministic for
|
|
* such allocations.
|
|
*/
|
|
if (random_right_allocate) {
|
|
/* Allocate on the "right" side, re-calculate address. */
|
|
meta->addr += PAGE_SIZE - size;
|
|
meta->addr = ALIGN_DOWN(meta->addr, cache->align);
|
|
}
|
|
|
|
addr = (void *)meta->addr;
|
|
|
|
/* Update remaining metadata. */
|
|
metadata_update_state(meta, KFENCE_OBJECT_ALLOCATED, stack_entries, num_stack_entries);
|
|
/* Pairs with READ_ONCE() in kfence_shutdown_cache(). */
|
|
WRITE_ONCE(meta->cache, cache);
|
|
meta->size = size;
|
|
meta->alloc_stack_hash = alloc_stack_hash;
|
|
raw_spin_unlock_irqrestore(&meta->lock, flags);
|
|
|
|
alloc_covered_add(alloc_stack_hash, 1);
|
|
|
|
/* Set required slab fields. */
|
|
slab = virt_to_slab((void *)meta->addr);
|
|
slab->slab_cache = cache;
|
|
#if defined(CONFIG_SLUB)
|
|
slab->objects = 1;
|
|
#elif defined(CONFIG_SLAB)
|
|
slab->s_mem = addr;
|
|
#endif
|
|
|
|
/* Memory initialization. */
|
|
set_canary(meta);
|
|
|
|
/*
|
|
* We check slab_want_init_on_alloc() ourselves, rather than letting
|
|
* SL*B do the initialization, as otherwise we might overwrite KFENCE's
|
|
* redzone.
|
|
*/
|
|
if (unlikely(slab_want_init_on_alloc(gfp, cache)))
|
|
memzero_explicit(addr, size);
|
|
if (cache->ctor)
|
|
cache->ctor(addr);
|
|
|
|
if (random_fault)
|
|
kfence_protect(meta->addr); /* Random "faults" by protecting the object. */
|
|
|
|
atomic_long_inc(&counters[KFENCE_COUNTER_ALLOCATED]);
|
|
atomic_long_inc(&counters[KFENCE_COUNTER_ALLOCS]);
|
|
|
|
return addr;
|
|
}
|
|
|
|
static void kfence_guarded_free(void *addr, struct kfence_metadata *meta, bool zombie)
|
|
{
|
|
struct kcsan_scoped_access assert_page_exclusive;
|
|
unsigned long flags;
|
|
bool init;
|
|
|
|
raw_spin_lock_irqsave(&meta->lock, flags);
|
|
|
|
if (meta->state != KFENCE_OBJECT_ALLOCATED || meta->addr != (unsigned long)addr) {
|
|
/* Invalid or double-free, bail out. */
|
|
atomic_long_inc(&counters[KFENCE_COUNTER_BUGS]);
|
|
kfence_report_error((unsigned long)addr, false, NULL, meta,
|
|
KFENCE_ERROR_INVALID_FREE);
|
|
raw_spin_unlock_irqrestore(&meta->lock, flags);
|
|
return;
|
|
}
|
|
|
|
/* Detect racy use-after-free, or incorrect reallocation of this page by KFENCE. */
|
|
kcsan_begin_scoped_access((void *)ALIGN_DOWN((unsigned long)addr, PAGE_SIZE), PAGE_SIZE,
|
|
KCSAN_ACCESS_SCOPED | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ASSERT,
|
|
&assert_page_exclusive);
|
|
|
|
if (CONFIG_KFENCE_STRESS_TEST_FAULTS)
|
|
kfence_unprotect((unsigned long)addr); /* To check canary bytes. */
|
|
|
|
/* Restore page protection if there was an OOB access. */
|
|
if (meta->unprotected_page) {
|
|
memzero_explicit((void *)ALIGN_DOWN(meta->unprotected_page, PAGE_SIZE), PAGE_SIZE);
|
|
kfence_protect(meta->unprotected_page);
|
|
meta->unprotected_page = 0;
|
|
}
|
|
|
|
/* Mark the object as freed. */
|
|
metadata_update_state(meta, KFENCE_OBJECT_FREED, NULL, 0);
|
|
init = slab_want_init_on_free(meta->cache);
|
|
raw_spin_unlock_irqrestore(&meta->lock, flags);
|
|
|
|
alloc_covered_add(meta->alloc_stack_hash, -1);
|
|
|
|
/* Check canary bytes for memory corruption. */
|
|
check_canary(meta);
|
|
|
|
/*
|
|
* Clear memory if init-on-free is set. While we protect the page, the
|
|
* data is still there, and after a use-after-free is detected, we
|
|
* unprotect the page, so the data is still accessible.
|
|
*/
|
|
if (!zombie && unlikely(init))
|
|
memzero_explicit(addr, meta->size);
|
|
|
|
/* Protect to detect use-after-frees. */
|
|
kfence_protect((unsigned long)addr);
|
|
|
|
kcsan_end_scoped_access(&assert_page_exclusive);
|
|
if (!zombie) {
|
|
/* Add it to the tail of the freelist for reuse. */
|
|
raw_spin_lock_irqsave(&kfence_freelist_lock, flags);
|
|
KFENCE_WARN_ON(!list_empty(&meta->list));
|
|
list_add_tail(&meta->list, &kfence_freelist);
|
|
raw_spin_unlock_irqrestore(&kfence_freelist_lock, flags);
|
|
|
|
atomic_long_dec(&counters[KFENCE_COUNTER_ALLOCATED]);
|
|
atomic_long_inc(&counters[KFENCE_COUNTER_FREES]);
|
|
} else {
|
|
/* See kfence_shutdown_cache(). */
|
|
atomic_long_inc(&counters[KFENCE_COUNTER_ZOMBIES]);
|
|
}
|
|
}
|
|
|
|
static void rcu_guarded_free(struct rcu_head *h)
|
|
{
|
|
struct kfence_metadata *meta = container_of(h, struct kfence_metadata, rcu_head);
|
|
|
|
kfence_guarded_free((void *)meta->addr, meta, false);
|
|
}
|
|
|
|
/*
|
|
* Initialization of the KFENCE pool after its allocation.
|
|
* Returns 0 on success; otherwise returns the address up to
|
|
* which partial initialization succeeded.
|
|
*/
|
|
static unsigned long kfence_init_pool(void)
|
|
{
|
|
unsigned long addr = (unsigned long)__kfence_pool;
|
|
struct page *pages;
|
|
int i;
|
|
|
|
if (!arch_kfence_init_pool())
|
|
return addr;
|
|
|
|
pages = virt_to_page(__kfence_pool);
|
|
|
|
/*
|
|
* Set up object pages: they must have PG_slab set, to avoid freeing
|
|
* these as real pages.
|
|
*
|
|
* We also want to avoid inserting kfence_free() in the kfree()
|
|
* fast-path in SLUB, and therefore need to ensure kfree() correctly
|
|
* enters __slab_free() slow-path.
|
|
*/
|
|
for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) {
|
|
struct slab *slab = page_slab(nth_page(pages, i));
|
|
|
|
if (!i || (i % 2))
|
|
continue;
|
|
|
|
__folio_set_slab(slab_folio(slab));
|
|
#ifdef CONFIG_MEMCG
|
|
slab->memcg_data = (unsigned long)&kfence_metadata[i / 2 - 1].objcg |
|
|
MEMCG_DATA_OBJCGS;
|
|
#endif
|
|
}
|
|
|
|
/*
|
|
* Protect the first 2 pages. The first page is mostly unnecessary, and
|
|
* merely serves as an extended guard page. However, adding one
|
|
* additional page in the beginning gives us an even number of pages,
|
|
* which simplifies the mapping of address to metadata index.
|
|
*/
|
|
for (i = 0; i < 2; i++) {
|
|
if (unlikely(!kfence_protect(addr)))
|
|
return addr;
|
|
|
|
addr += PAGE_SIZE;
|
|
}
|
|
|
|
for (i = 0; i < CONFIG_KFENCE_NUM_OBJECTS; i++) {
|
|
struct kfence_metadata *meta = &kfence_metadata[i];
|
|
|
|
/* Initialize metadata. */
|
|
INIT_LIST_HEAD(&meta->list);
|
|
raw_spin_lock_init(&meta->lock);
|
|
meta->state = KFENCE_OBJECT_UNUSED;
|
|
meta->addr = addr; /* Initialize for validation in metadata_to_pageaddr(). */
|
|
list_add_tail(&meta->list, &kfence_freelist);
|
|
|
|
/* Protect the right redzone. */
|
|
if (unlikely(!kfence_protect(addr + PAGE_SIZE)))
|
|
goto reset_slab;
|
|
|
|
addr += 2 * PAGE_SIZE;
|
|
}
|
|
|
|
return 0;
|
|
|
|
reset_slab:
|
|
for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) {
|
|
struct slab *slab = page_slab(nth_page(pages, i));
|
|
|
|
if (!i || (i % 2))
|
|
continue;
|
|
#ifdef CONFIG_MEMCG
|
|
slab->memcg_data = 0;
|
|
#endif
|
|
__folio_clear_slab(slab_folio(slab));
|
|
}
|
|
|
|
return addr;
|
|
}
|
|
|
|
static bool __init kfence_init_pool_early(void)
|
|
{
|
|
unsigned long addr;
|
|
|
|
if (!__kfence_pool)
|
|
return false;
|
|
|
|
addr = kfence_init_pool();
|
|
|
|
if (!addr) {
|
|
/*
|
|
* The pool is live and will never be deallocated from this point on.
|
|
* Ignore the pool object from the kmemleak phys object tree, as it would
|
|
* otherwise overlap with allocations returned by kfence_alloc(), which
|
|
* are registered with kmemleak through the slab post-alloc hook.
|
|
*/
|
|
kmemleak_ignore_phys(__pa(__kfence_pool));
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* Only release unprotected pages, and do not try to go back and change
|
|
* page attributes due to risk of failing to do so as well. If changing
|
|
* page attributes for some pages fails, it is very likely that it also
|
|
* fails for the first page, and therefore expect addr==__kfence_pool in
|
|
* most failure cases.
|
|
*/
|
|
memblock_free_late(__pa(addr), KFENCE_POOL_SIZE - (addr - (unsigned long)__kfence_pool));
|
|
__kfence_pool = NULL;
|
|
return false;
|
|
}
|
|
|
|
static bool kfence_init_pool_late(void)
|
|
{
|
|
unsigned long addr, free_size;
|
|
|
|
addr = kfence_init_pool();
|
|
|
|
if (!addr)
|
|
return true;
|
|
|
|
/* Same as above. */
|
|
free_size = KFENCE_POOL_SIZE - (addr - (unsigned long)__kfence_pool);
|
|
#ifdef CONFIG_CONTIG_ALLOC
|
|
free_contig_range(page_to_pfn(virt_to_page((void *)addr)), free_size / PAGE_SIZE);
|
|
#else
|
|
free_pages_exact((void *)addr, free_size);
|
|
#endif
|
|
__kfence_pool = NULL;
|
|
return false;
|
|
}
|
|
|
|
/* === DebugFS Interface ==================================================== */
|
|
|
|
static int stats_show(struct seq_file *seq, void *v)
|
|
{
|
|
int i;
|
|
|
|
seq_printf(seq, "enabled: %i\n", READ_ONCE(kfence_enabled));
|
|
for (i = 0; i < KFENCE_COUNTER_COUNT; i++)
|
|
seq_printf(seq, "%s: %ld\n", counter_names[i], atomic_long_read(&counters[i]));
|
|
|
|
return 0;
|
|
}
|
|
DEFINE_SHOW_ATTRIBUTE(stats);
|
|
|
|
/*
|
|
* debugfs seq_file operations for /sys/kernel/debug/kfence/objects.
|
|
* start_object() and next_object() return the object index + 1, because NULL is used
|
|
* to stop iteration.
|
|
*/
|
|
static void *start_object(struct seq_file *seq, loff_t *pos)
|
|
{
|
|
if (*pos < CONFIG_KFENCE_NUM_OBJECTS)
|
|
return (void *)((long)*pos + 1);
|
|
return NULL;
|
|
}
|
|
|
|
static void stop_object(struct seq_file *seq, void *v)
|
|
{
|
|
}
|
|
|
|
static void *next_object(struct seq_file *seq, void *v, loff_t *pos)
|
|
{
|
|
++*pos;
|
|
if (*pos < CONFIG_KFENCE_NUM_OBJECTS)
|
|
return (void *)((long)*pos + 1);
|
|
return NULL;
|
|
}
|
|
|
|
static int show_object(struct seq_file *seq, void *v)
|
|
{
|
|
struct kfence_metadata *meta = &kfence_metadata[(long)v - 1];
|
|
unsigned long flags;
|
|
|
|
raw_spin_lock_irqsave(&meta->lock, flags);
|
|
kfence_print_object(seq, meta);
|
|
raw_spin_unlock_irqrestore(&meta->lock, flags);
|
|
seq_puts(seq, "---------------------------------\n");
|
|
|
|
return 0;
|
|
}
|
|
|
|
static const struct seq_operations objects_sops = {
|
|
.start = start_object,
|
|
.next = next_object,
|
|
.stop = stop_object,
|
|
.show = show_object,
|
|
};
|
|
DEFINE_SEQ_ATTRIBUTE(objects);
|
|
|
|
static int kfence_debugfs_init(void)
|
|
{
|
|
struct dentry *kfence_dir;
|
|
|
|
if (!READ_ONCE(kfence_enabled))
|
|
return 0;
|
|
|
|
kfence_dir = debugfs_create_dir("kfence", NULL);
|
|
debugfs_create_file("stats", 0444, kfence_dir, NULL, &stats_fops);
|
|
debugfs_create_file("objects", 0400, kfence_dir, NULL, &objects_fops);
|
|
return 0;
|
|
}
|
|
|
|
late_initcall(kfence_debugfs_init);
|
|
|
|
/* === Panic Notifier ====================================================== */
|
|
|
|
static void kfence_check_all_canary(void)
|
|
{
|
|
int i;
|
|
|
|
for (i = 0; i < CONFIG_KFENCE_NUM_OBJECTS; i++) {
|
|
struct kfence_metadata *meta = &kfence_metadata[i];
|
|
|
|
if (meta->state == KFENCE_OBJECT_ALLOCATED)
|
|
check_canary(meta);
|
|
}
|
|
}
|
|
|
|
static int kfence_check_canary_callback(struct notifier_block *nb,
|
|
unsigned long reason, void *arg)
|
|
{
|
|
kfence_check_all_canary();
|
|
return NOTIFY_OK;
|
|
}
|
|
|
|
static struct notifier_block kfence_check_canary_notifier = {
|
|
.notifier_call = kfence_check_canary_callback,
|
|
};
|
|
|
|
/* === Allocation Gate Timer ================================================ */
|
|
|
|
static struct delayed_work kfence_timer;
|
|
|
|
#ifdef CONFIG_KFENCE_STATIC_KEYS
|
|
/* Wait queue to wake up allocation-gate timer task. */
|
|
static DECLARE_WAIT_QUEUE_HEAD(allocation_wait);
|
|
|
|
static void wake_up_kfence_timer(struct irq_work *work)
|
|
{
|
|
wake_up(&allocation_wait);
|
|
}
|
|
static DEFINE_IRQ_WORK(wake_up_kfence_timer_work, wake_up_kfence_timer);
|
|
#endif
|
|
|
|
/*
|
|
* Set up delayed work, which will enable and disable the static key. We need to
|
|
* use a work queue (rather than a simple timer), since enabling and disabling a
|
|
* static key cannot be done from an interrupt.
|
|
*
|
|
* Note: Toggling a static branch currently causes IPIs, and here we'll end up
|
|
* with a total of 2 IPIs to all CPUs. If this ends up a problem in future (with
|
|
* more aggressive sampling intervals), we could get away with a variant that
|
|
* avoids IPIs, at the cost of not immediately capturing allocations if the
|
|
* instructions remain cached.
|
|
*/
|
|
static void toggle_allocation_gate(struct work_struct *work)
|
|
{
|
|
if (!READ_ONCE(kfence_enabled))
|
|
return;
|
|
|
|
atomic_set(&kfence_allocation_gate, 0);
|
|
#ifdef CONFIG_KFENCE_STATIC_KEYS
|
|
/* Enable static key, and await allocation to happen. */
|
|
static_branch_enable(&kfence_allocation_key);
|
|
|
|
wait_event_idle(allocation_wait, atomic_read(&kfence_allocation_gate));
|
|
|
|
/* Disable static key and reset timer. */
|
|
static_branch_disable(&kfence_allocation_key);
|
|
#endif
|
|
queue_delayed_work(system_unbound_wq, &kfence_timer,
|
|
msecs_to_jiffies(kfence_sample_interval));
|
|
}
|
|
|
|
/* === Public interface ===================================================== */
|
|
|
|
void __init kfence_alloc_pool(void)
|
|
{
|
|
if (!kfence_sample_interval)
|
|
return;
|
|
|
|
/* if the pool has already been initialized by arch, skip the below. */
|
|
if (__kfence_pool)
|
|
return;
|
|
|
|
__kfence_pool = memblock_alloc(KFENCE_POOL_SIZE, PAGE_SIZE);
|
|
|
|
if (!__kfence_pool)
|
|
pr_err("failed to allocate pool\n");
|
|
}
|
|
|
|
static void kfence_init_enable(void)
|
|
{
|
|
if (!IS_ENABLED(CONFIG_KFENCE_STATIC_KEYS))
|
|
static_branch_enable(&kfence_allocation_key);
|
|
|
|
if (kfence_deferrable)
|
|
INIT_DEFERRABLE_WORK(&kfence_timer, toggle_allocation_gate);
|
|
else
|
|
INIT_DELAYED_WORK(&kfence_timer, toggle_allocation_gate);
|
|
|
|
if (kfence_check_on_panic)
|
|
atomic_notifier_chain_register(&panic_notifier_list, &kfence_check_canary_notifier);
|
|
|
|
WRITE_ONCE(kfence_enabled, true);
|
|
queue_delayed_work(system_unbound_wq, &kfence_timer, 0);
|
|
|
|
pr_info("initialized - using %lu bytes for %d objects at 0x%p-0x%p\n", KFENCE_POOL_SIZE,
|
|
CONFIG_KFENCE_NUM_OBJECTS, (void *)__kfence_pool,
|
|
(void *)(__kfence_pool + KFENCE_POOL_SIZE));
|
|
}
|
|
|
|
void __init kfence_init(void)
|
|
{
|
|
stack_hash_seed = get_random_u32();
|
|
|
|
/* Setting kfence_sample_interval to 0 on boot disables KFENCE. */
|
|
if (!kfence_sample_interval)
|
|
return;
|
|
|
|
if (!kfence_init_pool_early()) {
|
|
pr_err("%s failed\n", __func__);
|
|
return;
|
|
}
|
|
|
|
kfence_init_enable();
|
|
}
|
|
|
|
static int kfence_init_late(void)
|
|
{
|
|
const unsigned long nr_pages = KFENCE_POOL_SIZE / PAGE_SIZE;
|
|
#ifdef CONFIG_CONTIG_ALLOC
|
|
struct page *pages;
|
|
|
|
pages = alloc_contig_pages(nr_pages, GFP_KERNEL, first_online_node, NULL);
|
|
if (!pages)
|
|
return -ENOMEM;
|
|
__kfence_pool = page_to_virt(pages);
|
|
#else
|
|
if (nr_pages > MAX_ORDER_NR_PAGES) {
|
|
pr_warn("KFENCE_NUM_OBJECTS too large for buddy allocator\n");
|
|
return -EINVAL;
|
|
}
|
|
__kfence_pool = alloc_pages_exact(KFENCE_POOL_SIZE, GFP_KERNEL);
|
|
if (!__kfence_pool)
|
|
return -ENOMEM;
|
|
#endif
|
|
|
|
if (!kfence_init_pool_late()) {
|
|
pr_err("%s failed\n", __func__);
|
|
return -EBUSY;
|
|
}
|
|
|
|
kfence_init_enable();
|
|
kfence_debugfs_init();
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int kfence_enable_late(void)
|
|
{
|
|
if (!__kfence_pool)
|
|
return kfence_init_late();
|
|
|
|
WRITE_ONCE(kfence_enabled, true);
|
|
queue_delayed_work(system_unbound_wq, &kfence_timer, 0);
|
|
pr_info("re-enabled\n");
|
|
return 0;
|
|
}
|
|
|
|
void kfence_shutdown_cache(struct kmem_cache *s)
|
|
{
|
|
unsigned long flags;
|
|
struct kfence_metadata *meta;
|
|
int i;
|
|
|
|
for (i = 0; i < CONFIG_KFENCE_NUM_OBJECTS; i++) {
|
|
bool in_use;
|
|
|
|
meta = &kfence_metadata[i];
|
|
|
|
/*
|
|
* If we observe some inconsistent cache and state pair where we
|
|
* should have returned false here, cache destruction is racing
|
|
* with either kmem_cache_alloc() or kmem_cache_free(). Taking
|
|
* the lock will not help, as different critical section
|
|
* serialization will have the same outcome.
|
|
*/
|
|
if (READ_ONCE(meta->cache) != s ||
|
|
READ_ONCE(meta->state) != KFENCE_OBJECT_ALLOCATED)
|
|
continue;
|
|
|
|
raw_spin_lock_irqsave(&meta->lock, flags);
|
|
in_use = meta->cache == s && meta->state == KFENCE_OBJECT_ALLOCATED;
|
|
raw_spin_unlock_irqrestore(&meta->lock, flags);
|
|
|
|
if (in_use) {
|
|
/*
|
|
* This cache still has allocations, and we should not
|
|
* release them back into the freelist so they can still
|
|
* safely be used and retain the kernel's default
|
|
* behaviour of keeping the allocations alive (leak the
|
|
* cache); however, they effectively become "zombie
|
|
* allocations" as the KFENCE objects are the only ones
|
|
* still in use and the owning cache is being destroyed.
|
|
*
|
|
* We mark them freed, so that any subsequent use shows
|
|
* more useful error messages that will include stack
|
|
* traces of the user of the object, the original
|
|
* allocation, and caller to shutdown_cache().
|
|
*/
|
|
kfence_guarded_free((void *)meta->addr, meta, /*zombie=*/true);
|
|
}
|
|
}
|
|
|
|
for (i = 0; i < CONFIG_KFENCE_NUM_OBJECTS; i++) {
|
|
meta = &kfence_metadata[i];
|
|
|
|
/* See above. */
|
|
if (READ_ONCE(meta->cache) != s || READ_ONCE(meta->state) != KFENCE_OBJECT_FREED)
|
|
continue;
|
|
|
|
raw_spin_lock_irqsave(&meta->lock, flags);
|
|
if (meta->cache == s && meta->state == KFENCE_OBJECT_FREED)
|
|
meta->cache = NULL;
|
|
raw_spin_unlock_irqrestore(&meta->lock, flags);
|
|
}
|
|
}
|
|
|
|
void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags)
|
|
{
|
|
unsigned long stack_entries[KFENCE_STACK_DEPTH];
|
|
size_t num_stack_entries;
|
|
u32 alloc_stack_hash;
|
|
|
|
/*
|
|
* Perform size check before switching kfence_allocation_gate, so that
|
|
* we don't disable KFENCE without making an allocation.
|
|
*/
|
|
if (size > PAGE_SIZE) {
|
|
atomic_long_inc(&counters[KFENCE_COUNTER_SKIP_INCOMPAT]);
|
|
return NULL;
|
|
}
|
|
|
|
/*
|
|
* Skip allocations from non-default zones, including DMA. We cannot
|
|
* guarantee that pages in the KFENCE pool will have the requested
|
|
* properties (e.g. reside in DMAable memory).
|
|
*/
|
|
if ((flags & GFP_ZONEMASK) ||
|
|
(s->flags & (SLAB_CACHE_DMA | SLAB_CACHE_DMA32))) {
|
|
atomic_long_inc(&counters[KFENCE_COUNTER_SKIP_INCOMPAT]);
|
|
return NULL;
|
|
}
|
|
|
|
/*
|
|
* Skip allocations for this slab, if KFENCE has been disabled for
|
|
* this slab.
|
|
*/
|
|
if (s->flags & SLAB_SKIP_KFENCE)
|
|
return NULL;
|
|
|
|
if (atomic_inc_return(&kfence_allocation_gate) > 1)
|
|
return NULL;
|
|
#ifdef CONFIG_KFENCE_STATIC_KEYS
|
|
/*
|
|
* waitqueue_active() is fully ordered after the update of
|
|
* kfence_allocation_gate per atomic_inc_return().
|
|
*/
|
|
if (waitqueue_active(&allocation_wait)) {
|
|
/*
|
|
* Calling wake_up() here may deadlock when allocations happen
|
|
* from within timer code. Use an irq_work to defer it.
|
|
*/
|
|
irq_work_queue(&wake_up_kfence_timer_work);
|
|
}
|
|
#endif
|
|
|
|
if (!READ_ONCE(kfence_enabled))
|
|
return NULL;
|
|
|
|
num_stack_entries = stack_trace_save(stack_entries, KFENCE_STACK_DEPTH, 0);
|
|
|
|
/*
|
|
* Do expensive check for coverage of allocation in slow-path after
|
|
* allocation_gate has already become non-zero, even though it might
|
|
* mean not making any allocation within a given sample interval.
|
|
*
|
|
* This ensures reasonable allocation coverage when the pool is almost
|
|
* full, including avoiding long-lived allocations of the same source
|
|
* filling up the pool (e.g. pagecache allocations).
|
|
*/
|
|
alloc_stack_hash = get_alloc_stack_hash(stack_entries, num_stack_entries);
|
|
if (should_skip_covered() && alloc_covered_contains(alloc_stack_hash)) {
|
|
atomic_long_inc(&counters[KFENCE_COUNTER_SKIP_COVERED]);
|
|
return NULL;
|
|
}
|
|
|
|
return kfence_guarded_alloc(s, size, flags, stack_entries, num_stack_entries,
|
|
alloc_stack_hash);
|
|
}
|
|
|
|
size_t kfence_ksize(const void *addr)
|
|
{
|
|
const struct kfence_metadata *meta = addr_to_metadata((unsigned long)addr);
|
|
|
|
/*
|
|
* Read locklessly -- if there is a race with __kfence_alloc(), this is
|
|
* either a use-after-free or invalid access.
|
|
*/
|
|
return meta ? meta->size : 0;
|
|
}
|
|
|
|
void *kfence_object_start(const void *addr)
|
|
{
|
|
const struct kfence_metadata *meta = addr_to_metadata((unsigned long)addr);
|
|
|
|
/*
|
|
* Read locklessly -- if there is a race with __kfence_alloc(), this is
|
|
* either a use-after-free or invalid access.
|
|
*/
|
|
return meta ? (void *)meta->addr : NULL;
|
|
}
|
|
|
|
void __kfence_free(void *addr)
|
|
{
|
|
struct kfence_metadata *meta = addr_to_metadata((unsigned long)addr);
|
|
|
|
#ifdef CONFIG_MEMCG
|
|
KFENCE_WARN_ON(meta->objcg);
|
|
#endif
|
|
/*
|
|
* If the objects of the cache are SLAB_TYPESAFE_BY_RCU, defer freeing
|
|
* the object, as the object page may be recycled for other-typed
|
|
* objects once it has been freed. meta->cache may be NULL if the cache
|
|
* was destroyed.
|
|
*/
|
|
if (unlikely(meta->cache && (meta->cache->flags & SLAB_TYPESAFE_BY_RCU)))
|
|
call_rcu(&meta->rcu_head, rcu_guarded_free);
|
|
else
|
|
kfence_guarded_free(addr, meta, false);
|
|
}
|
|
|
|
bool kfence_handle_page_fault(unsigned long addr, bool is_write, struct pt_regs *regs)
|
|
{
|
|
const int page_index = (addr - (unsigned long)__kfence_pool) / PAGE_SIZE;
|
|
struct kfence_metadata *to_report = NULL;
|
|
enum kfence_error_type error_type;
|
|
unsigned long flags;
|
|
|
|
if (!is_kfence_address((void *)addr))
|
|
return false;
|
|
|
|
if (!READ_ONCE(kfence_enabled)) /* If disabled at runtime ... */
|
|
return kfence_unprotect(addr); /* ... unprotect and proceed. */
|
|
|
|
atomic_long_inc(&counters[KFENCE_COUNTER_BUGS]);
|
|
|
|
if (page_index % 2) {
|
|
/* This is a redzone, report a buffer overflow. */
|
|
struct kfence_metadata *meta;
|
|
int distance = 0;
|
|
|
|
meta = addr_to_metadata(addr - PAGE_SIZE);
|
|
if (meta && READ_ONCE(meta->state) == KFENCE_OBJECT_ALLOCATED) {
|
|
to_report = meta;
|
|
/* Data race ok; distance calculation approximate. */
|
|
distance = addr - data_race(meta->addr + meta->size);
|
|
}
|
|
|
|
meta = addr_to_metadata(addr + PAGE_SIZE);
|
|
if (meta && READ_ONCE(meta->state) == KFENCE_OBJECT_ALLOCATED) {
|
|
/* Data race ok; distance calculation approximate. */
|
|
if (!to_report || distance > data_race(meta->addr) - addr)
|
|
to_report = meta;
|
|
}
|
|
|
|
if (!to_report)
|
|
goto out;
|
|
|
|
raw_spin_lock_irqsave(&to_report->lock, flags);
|
|
to_report->unprotected_page = addr;
|
|
error_type = KFENCE_ERROR_OOB;
|
|
|
|
/*
|
|
* If the object was freed before we took the look we can still
|
|
* report this as an OOB -- the report will simply show the
|
|
* stacktrace of the free as well.
|
|
*/
|
|
} else {
|
|
to_report = addr_to_metadata(addr);
|
|
if (!to_report)
|
|
goto out;
|
|
|
|
raw_spin_lock_irqsave(&to_report->lock, flags);
|
|
error_type = KFENCE_ERROR_UAF;
|
|
/*
|
|
* We may race with __kfence_alloc(), and it is possible that a
|
|
* freed object may be reallocated. We simply report this as a
|
|
* use-after-free, with the stack trace showing the place where
|
|
* the object was re-allocated.
|
|
*/
|
|
}
|
|
|
|
out:
|
|
if (to_report) {
|
|
kfence_report_error(addr, is_write, regs, to_report, error_type);
|
|
raw_spin_unlock_irqrestore(&to_report->lock, flags);
|
|
} else {
|
|
/* This may be a UAF or OOB access, but we can't be sure. */
|
|
kfence_report_error(addr, is_write, regs, NULL, KFENCE_ERROR_INVALID);
|
|
}
|
|
|
|
return kfence_unprotect(addr); /* Unprotect and let access proceed. */
|
|
}
|