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![Mike Rapoport](/assets/img/avatar_default.png)
Introduce "memfd_secret" system call with the ability to create memory
areas visible only in the context of the owning process and not mapped not
only to other processes but in the kernel page tables as well.
The secretmem feature is off by default and the user must explicitly
enable it at the boot time.
Once secretmem is enabled, the user will be able to create a file
descriptor using the memfd_secret() system call. The memory areas created
by mmap() calls from this file descriptor will be unmapped from the kernel
direct map and they will be only mapped in the page table of the processes
that have access to the file descriptor.
Secretmem is designed to provide the following protections:
* Enhanced protection (in conjunction with all the other in-kernel
attack prevention systems) against ROP attacks. Seceretmem makes
"simple" ROP insufficient to perform exfiltration, which increases the
required complexity of the attack. Along with other protections like
the kernel stack size limit and address space layout randomization which
make finding gadgets is really hard, absence of any in-kernel primitive
for accessing secret memory means the one gadget ROP attack can't work.
Since the only way to access secret memory is to reconstruct the missing
mapping entry, the attacker has to recover the physical page and insert
a PTE pointing to it in the kernel and then retrieve the contents. That
takes at least three gadgets which is a level of difficulty beyond most
standard attacks.
* Prevent cross-process secret userspace memory exposures. Once the
secret memory is allocated, the user can't accidentally pass it into the
kernel to be transmitted somewhere. The secreremem pages cannot be
accessed via the direct map and they are disallowed in GUP.
* Harden against exploited kernel flaws. In order to access secretmem,
a kernel-side attack would need to either walk the page tables and
create new ones, or spawn a new privileged uiserspace process to perform
secrets exfiltration using ptrace.
The file descriptor based memory has several advantages over the
"traditional" mm interfaces, such as mlock(), mprotect(), madvise(). File
descriptor approach allows explicit and controlled sharing of the memory
areas, it allows to seal the operations. Besides, file descriptor based
memory paves the way for VMMs to remove the secret memory range from the
userspace hipervisor process, for instance QEMU. Andy Lutomirski says:
"Getting fd-backed memory into a guest will take some possibly major
work in the kernel, but getting vma-backed memory into a guest without
mapping it in the host user address space seems much, much worse."
memfd_secret() is made a dedicated system call rather than an extension to
memfd_create() because it's purpose is to allow the user to create more
secure memory mappings rather than to simply allow file based access to
the memory. Nowadays a new system call cost is negligible while it is way
simpler for userspace to deal with a clear-cut system calls than with a
multiplexer or an overloaded syscall. Moreover, the initial
implementation of memfd_secret() is completely distinct from
memfd_create() so there is no much sense in overloading memfd_create() to
begin with. If there will be a need for code sharing between these
implementation it can be easily achieved without a need to adjust user
visible APIs.
The secret memory remains accessible in the process context using uaccess
primitives, but it is not exposed to the kernel otherwise; secret memory
areas are removed from the direct map and functions in the
follow_page()/get_user_page() family will refuse to return a page that
belongs to the secret memory area.
Once there will be a use case that will require exposing secretmem to the
kernel it will be an opt-in request in the system call flags so that user
would have to decide what data can be exposed to the kernel.
Removing of the pages from the direct map may cause its fragmentation on
architectures that use large pages to map the physical memory which
affects the system performance. However, the original Kconfig text for
CONFIG_DIRECT_GBPAGES said that gigabyte pages in the direct map "... can
improve the kernel's performance a tiny bit ..." (commit 00d1c5e057
("x86: add gbpages switches")) and the recent report [1] showed that "...
although 1G mappings are a good default choice, there is no compelling
evidence that it must be the only choice". Hence, it is sufficient to
have secretmem disabled by default with the ability of a system
administrator to enable it at boot time.
Pages in the secretmem regions are unevictable and unmovable to avoid
accidental exposure of the sensitive data via swap or during page
migration.
Since the secretmem mappings are locked in memory they cannot exceed
RLIMIT_MEMLOCK. Since these mappings are already locked independently
from mlock(), an attempt to mlock()/munlock() secretmem range would fail
and mlockall()/munlockall() will ignore secretmem mappings.
However, unlike mlock()ed memory, secretmem currently behaves more like
long-term GUP: secretmem mappings are unmovable mappings directly consumed
by user space. With default limits, there is no excessive use of
secretmem and it poses no real problem in combination with
ZONE_MOVABLE/CMA, but in the future this should be addressed to allow
balanced use of large amounts of secretmem along with ZONE_MOVABLE/CMA.
A page that was a part of the secret memory area is cleared when it is
freed to ensure the data is not exposed to the next user of that page.
The following example demonstrates creation of a secret mapping (error
handling is omitted):
fd = memfd_secret(0);
ftruncate(fd, MAP_SIZE);
ptr = mmap(NULL, MAP_SIZE, PROT_READ | PROT_WRITE,
MAP_SHARED, fd, 0);
[1] https://lore.kernel.org/linux-mm/213b4567-46ce-f116-9cdf-bbd0c884eb3c@linux.intel.com/
[akpm@linux-foundation.org: suppress Kconfig whine]
Link: https://lkml.kernel.org/r/20210518072034.31572-5-rppt@kernel.org
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Hagen Paul Pfeifer <hagen@jauu.net>
Acked-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christopher Lameter <cl@linux.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Elena Reshetova <elena.reshetova@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Palmer Dabbelt <palmerdabbelt@google.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tycho Andersen <tycho@tycho.ws>
Cc: Will Deacon <will@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: kernel test robot <lkp@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
855 lines
22 KiB
C
855 lines
22 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* linux/mm/mlock.c
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*
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* (C) Copyright 1995 Linus Torvalds
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* (C) Copyright 2002 Christoph Hellwig
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*/
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#include <linux/capability.h>
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#include <linux/mman.h>
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#include <linux/mm.h>
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#include <linux/sched/user.h>
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#include <linux/swap.h>
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#include <linux/swapops.h>
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#include <linux/pagemap.h>
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#include <linux/pagevec.h>
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#include <linux/mempolicy.h>
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#include <linux/syscalls.h>
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#include <linux/sched.h>
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#include <linux/export.h>
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#include <linux/rmap.h>
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#include <linux/mmzone.h>
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#include <linux/hugetlb.h>
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#include <linux/memcontrol.h>
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#include <linux/mm_inline.h>
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#include <linux/secretmem.h>
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#include "internal.h"
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bool can_do_mlock(void)
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{
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if (rlimit(RLIMIT_MEMLOCK) != 0)
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return true;
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if (capable(CAP_IPC_LOCK))
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return true;
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return false;
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}
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EXPORT_SYMBOL(can_do_mlock);
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/*
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* Mlocked pages are marked with PageMlocked() flag for efficient testing
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* in vmscan and, possibly, the fault path; and to support semi-accurate
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* statistics.
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*
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* An mlocked page [PageMlocked(page)] is unevictable. As such, it will
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* be placed on the LRU "unevictable" list, rather than the [in]active lists.
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* The unevictable list is an LRU sibling list to the [in]active lists.
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* PageUnevictable is set to indicate the unevictable state.
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*
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* When lazy mlocking via vmscan, it is important to ensure that the
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* vma's VM_LOCKED status is not concurrently being modified, otherwise we
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* may have mlocked a page that is being munlocked. So lazy mlock must take
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* the mmap_lock for read, and verify that the vma really is locked
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* (see mm/rmap.c).
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*/
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/*
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* LRU accounting for clear_page_mlock()
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*/
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void clear_page_mlock(struct page *page)
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{
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int nr_pages;
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if (!TestClearPageMlocked(page))
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return;
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nr_pages = thp_nr_pages(page);
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mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
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count_vm_events(UNEVICTABLE_PGCLEARED, nr_pages);
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/*
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* The previous TestClearPageMlocked() corresponds to the smp_mb()
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* in __pagevec_lru_add_fn().
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*
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* See __pagevec_lru_add_fn for more explanation.
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*/
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if (!isolate_lru_page(page)) {
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putback_lru_page(page);
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} else {
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/*
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* We lost the race. the page already moved to evictable list.
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*/
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if (PageUnevictable(page))
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count_vm_events(UNEVICTABLE_PGSTRANDED, nr_pages);
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}
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}
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/*
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* Mark page as mlocked if not already.
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* If page on LRU, isolate and putback to move to unevictable list.
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*/
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void mlock_vma_page(struct page *page)
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{
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/* Serialize with page migration */
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BUG_ON(!PageLocked(page));
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VM_BUG_ON_PAGE(PageTail(page), page);
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VM_BUG_ON_PAGE(PageCompound(page) && PageDoubleMap(page), page);
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if (!TestSetPageMlocked(page)) {
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int nr_pages = thp_nr_pages(page);
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mod_zone_page_state(page_zone(page), NR_MLOCK, nr_pages);
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count_vm_events(UNEVICTABLE_PGMLOCKED, nr_pages);
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if (!isolate_lru_page(page))
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putback_lru_page(page);
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}
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}
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/*
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* Finish munlock after successful page isolation
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*
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* Page must be locked. This is a wrapper for page_mlock()
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* and putback_lru_page() with munlock accounting.
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*/
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static void __munlock_isolated_page(struct page *page)
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{
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/*
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* Optimization: if the page was mapped just once, that's our mapping
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* and we don't need to check all the other vmas.
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*/
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if (page_mapcount(page) > 1)
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page_mlock(page);
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/* Did try_to_unlock() succeed or punt? */
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if (!PageMlocked(page))
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count_vm_events(UNEVICTABLE_PGMUNLOCKED, thp_nr_pages(page));
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putback_lru_page(page);
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}
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/*
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* Accounting for page isolation fail during munlock
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*
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* Performs accounting when page isolation fails in munlock. There is nothing
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* else to do because it means some other task has already removed the page
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* from the LRU. putback_lru_page() will take care of removing the page from
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* the unevictable list, if necessary. vmscan [page_referenced()] will move
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* the page back to the unevictable list if some other vma has it mlocked.
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*/
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static void __munlock_isolation_failed(struct page *page)
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{
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int nr_pages = thp_nr_pages(page);
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if (PageUnevictable(page))
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__count_vm_events(UNEVICTABLE_PGSTRANDED, nr_pages);
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else
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__count_vm_events(UNEVICTABLE_PGMUNLOCKED, nr_pages);
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}
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/**
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* munlock_vma_page - munlock a vma page
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* @page: page to be unlocked, either a normal page or THP page head
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*
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* returns the size of the page as a page mask (0 for normal page,
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* HPAGE_PMD_NR - 1 for THP head page)
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*
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* called from munlock()/munmap() path with page supposedly on the LRU.
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* When we munlock a page, because the vma where we found the page is being
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* munlock()ed or munmap()ed, we want to check whether other vmas hold the
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* page locked so that we can leave it on the unevictable lru list and not
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* bother vmscan with it. However, to walk the page's rmap list in
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* page_mlock() we must isolate the page from the LRU. If some other
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* task has removed the page from the LRU, we won't be able to do that.
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* So we clear the PageMlocked as we might not get another chance. If we
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* can't isolate the page, we leave it for putback_lru_page() and vmscan
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* [page_referenced()/try_to_unmap()] to deal with.
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*/
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unsigned int munlock_vma_page(struct page *page)
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{
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int nr_pages;
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/* For page_mlock() and to serialize with page migration */
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BUG_ON(!PageLocked(page));
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VM_BUG_ON_PAGE(PageTail(page), page);
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if (!TestClearPageMlocked(page)) {
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/* Potentially, PTE-mapped THP: do not skip the rest PTEs */
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return 0;
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}
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nr_pages = thp_nr_pages(page);
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mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
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if (!isolate_lru_page(page))
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__munlock_isolated_page(page);
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else
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__munlock_isolation_failed(page);
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return nr_pages - 1;
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}
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/*
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* convert get_user_pages() return value to posix mlock() error
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*/
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static int __mlock_posix_error_return(long retval)
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{
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if (retval == -EFAULT)
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retval = -ENOMEM;
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else if (retval == -ENOMEM)
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retval = -EAGAIN;
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return retval;
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}
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/*
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* Prepare page for fast batched LRU putback via putback_lru_evictable_pagevec()
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*
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* The fast path is available only for evictable pages with single mapping.
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* Then we can bypass the per-cpu pvec and get better performance.
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* when mapcount > 1 we need page_mlock() which can fail.
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* when !page_evictable(), we need the full redo logic of putback_lru_page to
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* avoid leaving evictable page in unevictable list.
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*
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* In case of success, @page is added to @pvec and @pgrescued is incremented
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* in case that the page was previously unevictable. @page is also unlocked.
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*/
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static bool __putback_lru_fast_prepare(struct page *page, struct pagevec *pvec,
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int *pgrescued)
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{
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VM_BUG_ON_PAGE(PageLRU(page), page);
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VM_BUG_ON_PAGE(!PageLocked(page), page);
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if (page_mapcount(page) <= 1 && page_evictable(page)) {
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pagevec_add(pvec, page);
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if (TestClearPageUnevictable(page))
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(*pgrescued)++;
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unlock_page(page);
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return true;
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}
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return false;
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}
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/*
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* Putback multiple evictable pages to the LRU
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*
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* Batched putback of evictable pages that bypasses the per-cpu pvec. Some of
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* the pages might have meanwhile become unevictable but that is OK.
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*/
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static void __putback_lru_fast(struct pagevec *pvec, int pgrescued)
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{
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count_vm_events(UNEVICTABLE_PGMUNLOCKED, pagevec_count(pvec));
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/*
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*__pagevec_lru_add() calls release_pages() so we don't call
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* put_page() explicitly
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*/
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__pagevec_lru_add(pvec);
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count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
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}
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/*
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* Munlock a batch of pages from the same zone
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*
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* The work is split to two main phases. First phase clears the Mlocked flag
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* and attempts to isolate the pages, all under a single zone lru lock.
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* The second phase finishes the munlock only for pages where isolation
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* succeeded.
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*
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* Note that the pagevec may be modified during the process.
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*/
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static void __munlock_pagevec(struct pagevec *pvec, struct zone *zone)
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{
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int i;
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int nr = pagevec_count(pvec);
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int delta_munlocked = -nr;
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struct pagevec pvec_putback;
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struct lruvec *lruvec = NULL;
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int pgrescued = 0;
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pagevec_init(&pvec_putback);
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/* Phase 1: page isolation */
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for (i = 0; i < nr; i++) {
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struct page *page = pvec->pages[i];
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if (TestClearPageMlocked(page)) {
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/*
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* We already have pin from follow_page_mask()
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* so we can spare the get_page() here.
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*/
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if (TestClearPageLRU(page)) {
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lruvec = relock_page_lruvec_irq(page, lruvec);
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del_page_from_lru_list(page, lruvec);
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continue;
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} else
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__munlock_isolation_failed(page);
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} else {
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delta_munlocked++;
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}
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/*
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* We won't be munlocking this page in the next phase
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* but we still need to release the follow_page_mask()
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* pin. We cannot do it under lru_lock however. If it's
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* the last pin, __page_cache_release() would deadlock.
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*/
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pagevec_add(&pvec_putback, pvec->pages[i]);
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pvec->pages[i] = NULL;
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}
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if (lruvec) {
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__mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
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unlock_page_lruvec_irq(lruvec);
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} else if (delta_munlocked) {
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mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
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}
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/* Now we can release pins of pages that we are not munlocking */
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pagevec_release(&pvec_putback);
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/* Phase 2: page munlock */
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for (i = 0; i < nr; i++) {
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struct page *page = pvec->pages[i];
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if (page) {
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lock_page(page);
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if (!__putback_lru_fast_prepare(page, &pvec_putback,
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&pgrescued)) {
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/*
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* Slow path. We don't want to lose the last
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* pin before unlock_page()
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*/
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get_page(page); /* for putback_lru_page() */
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__munlock_isolated_page(page);
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unlock_page(page);
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put_page(page); /* from follow_page_mask() */
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}
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}
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}
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/*
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* Phase 3: page putback for pages that qualified for the fast path
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* This will also call put_page() to return pin from follow_page_mask()
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*/
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if (pagevec_count(&pvec_putback))
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__putback_lru_fast(&pvec_putback, pgrescued);
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}
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/*
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* Fill up pagevec for __munlock_pagevec using pte walk
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*
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* The function expects that the struct page corresponding to @start address is
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* a non-TPH page already pinned and in the @pvec, and that it belongs to @zone.
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*
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* The rest of @pvec is filled by subsequent pages within the same pmd and same
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* zone, as long as the pte's are present and vm_normal_page() succeeds. These
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* pages also get pinned.
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*
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* Returns the address of the next page that should be scanned. This equals
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* @start + PAGE_SIZE when no page could be added by the pte walk.
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*/
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static unsigned long __munlock_pagevec_fill(struct pagevec *pvec,
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struct vm_area_struct *vma, struct zone *zone,
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|
unsigned long start, unsigned long end)
|
|
{
|
|
pte_t *pte;
|
|
spinlock_t *ptl;
|
|
|
|
/*
|
|
* Initialize pte walk starting at the already pinned page where we
|
|
* are sure that there is a pte, as it was pinned under the same
|
|
* mmap_lock write op.
|
|
*/
|
|
pte = get_locked_pte(vma->vm_mm, start, &ptl);
|
|
/* Make sure we do not cross the page table boundary */
|
|
end = pgd_addr_end(start, end);
|
|
end = p4d_addr_end(start, end);
|
|
end = pud_addr_end(start, end);
|
|
end = pmd_addr_end(start, end);
|
|
|
|
/* The page next to the pinned page is the first we will try to get */
|
|
start += PAGE_SIZE;
|
|
while (start < end) {
|
|
struct page *page = NULL;
|
|
pte++;
|
|
if (pte_present(*pte))
|
|
page = vm_normal_page(vma, start, *pte);
|
|
/*
|
|
* Break if page could not be obtained or the page's node+zone does not
|
|
* match
|
|
*/
|
|
if (!page || page_zone(page) != zone)
|
|
break;
|
|
|
|
/*
|
|
* Do not use pagevec for PTE-mapped THP,
|
|
* munlock_vma_pages_range() will handle them.
|
|
*/
|
|
if (PageTransCompound(page))
|
|
break;
|
|
|
|
get_page(page);
|
|
/*
|
|
* Increase the address that will be returned *before* the
|
|
* eventual break due to pvec becoming full by adding the page
|
|
*/
|
|
start += PAGE_SIZE;
|
|
if (pagevec_add(pvec, page) == 0)
|
|
break;
|
|
}
|
|
pte_unmap_unlock(pte, ptl);
|
|
return start;
|
|
}
|
|
|
|
/*
|
|
* munlock_vma_pages_range() - munlock all pages in the vma range.'
|
|
* @vma - vma containing range to be munlock()ed.
|
|
* @start - start address in @vma of the range
|
|
* @end - end of range in @vma.
|
|
*
|
|
* For mremap(), munmap() and exit().
|
|
*
|
|
* Called with @vma VM_LOCKED.
|
|
*
|
|
* Returns with VM_LOCKED cleared. Callers must be prepared to
|
|
* deal with this.
|
|
*
|
|
* We don't save and restore VM_LOCKED here because pages are
|
|
* still on lru. In unmap path, pages might be scanned by reclaim
|
|
* and re-mlocked by page_mlock/try_to_unmap before we unmap and
|
|
* free them. This will result in freeing mlocked pages.
|
|
*/
|
|
void munlock_vma_pages_range(struct vm_area_struct *vma,
|
|
unsigned long start, unsigned long end)
|
|
{
|
|
vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
|
|
|
|
while (start < end) {
|
|
struct page *page;
|
|
unsigned int page_mask = 0;
|
|
unsigned long page_increm;
|
|
struct pagevec pvec;
|
|
struct zone *zone;
|
|
|
|
pagevec_init(&pvec);
|
|
/*
|
|
* Although FOLL_DUMP is intended for get_dump_page(),
|
|
* it just so happens that its special treatment of the
|
|
* ZERO_PAGE (returning an error instead of doing get_page)
|
|
* suits munlock very well (and if somehow an abnormal page
|
|
* has sneaked into the range, we won't oops here: great).
|
|
*/
|
|
page = follow_page(vma, start, FOLL_GET | FOLL_DUMP);
|
|
|
|
if (page && !IS_ERR(page)) {
|
|
if (PageTransTail(page)) {
|
|
VM_BUG_ON_PAGE(PageMlocked(page), page);
|
|
put_page(page); /* follow_page_mask() */
|
|
} else if (PageTransHuge(page)) {
|
|
lock_page(page);
|
|
/*
|
|
* Any THP page found by follow_page_mask() may
|
|
* have gotten split before reaching
|
|
* munlock_vma_page(), so we need to compute
|
|
* the page_mask here instead.
|
|
*/
|
|
page_mask = munlock_vma_page(page);
|
|
unlock_page(page);
|
|
put_page(page); /* follow_page_mask() */
|
|
} else {
|
|
/*
|
|
* Non-huge pages are handled in batches via
|
|
* pagevec. The pin from follow_page_mask()
|
|
* prevents them from collapsing by THP.
|
|
*/
|
|
pagevec_add(&pvec, page);
|
|
zone = page_zone(page);
|
|
|
|
/*
|
|
* Try to fill the rest of pagevec using fast
|
|
* pte walk. This will also update start to
|
|
* the next page to process. Then munlock the
|
|
* pagevec.
|
|
*/
|
|
start = __munlock_pagevec_fill(&pvec, vma,
|
|
zone, start, end);
|
|
__munlock_pagevec(&pvec, zone);
|
|
goto next;
|
|
}
|
|
}
|
|
page_increm = 1 + page_mask;
|
|
start += page_increm * PAGE_SIZE;
|
|
next:
|
|
cond_resched();
|
|
}
|
|
}
|
|
|
|
/*
|
|
* mlock_fixup - handle mlock[all]/munlock[all] requests.
|
|
*
|
|
* Filters out "special" vmas -- VM_LOCKED never gets set for these, and
|
|
* munlock is a no-op. However, for some special vmas, we go ahead and
|
|
* populate the ptes.
|
|
*
|
|
* For vmas that pass the filters, merge/split as appropriate.
|
|
*/
|
|
static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
|
|
unsigned long start, unsigned long end, vm_flags_t newflags)
|
|
{
|
|
struct mm_struct *mm = vma->vm_mm;
|
|
pgoff_t pgoff;
|
|
int nr_pages;
|
|
int ret = 0;
|
|
int lock = !!(newflags & VM_LOCKED);
|
|
vm_flags_t old_flags = vma->vm_flags;
|
|
|
|
if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
|
|
is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm) ||
|
|
vma_is_dax(vma) || vma_is_secretmem(vma))
|
|
/* don't set VM_LOCKED or VM_LOCKONFAULT and don't count */
|
|
goto out;
|
|
|
|
pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
|
|
*prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
|
|
vma->vm_file, pgoff, vma_policy(vma),
|
|
vma->vm_userfaultfd_ctx);
|
|
if (*prev) {
|
|
vma = *prev;
|
|
goto success;
|
|
}
|
|
|
|
if (start != vma->vm_start) {
|
|
ret = split_vma(mm, vma, start, 1);
|
|
if (ret)
|
|
goto out;
|
|
}
|
|
|
|
if (end != vma->vm_end) {
|
|
ret = split_vma(mm, vma, end, 0);
|
|
if (ret)
|
|
goto out;
|
|
}
|
|
|
|
success:
|
|
/*
|
|
* Keep track of amount of locked VM.
|
|
*/
|
|
nr_pages = (end - start) >> PAGE_SHIFT;
|
|
if (!lock)
|
|
nr_pages = -nr_pages;
|
|
else if (old_flags & VM_LOCKED)
|
|
nr_pages = 0;
|
|
mm->locked_vm += nr_pages;
|
|
|
|
/*
|
|
* vm_flags is protected by the mmap_lock held in write mode.
|
|
* It's okay if try_to_unmap_one unmaps a page just after we
|
|
* set VM_LOCKED, populate_vma_page_range will bring it back.
|
|
*/
|
|
|
|
if (lock)
|
|
vma->vm_flags = newflags;
|
|
else
|
|
munlock_vma_pages_range(vma, start, end);
|
|
|
|
out:
|
|
*prev = vma;
|
|
return ret;
|
|
}
|
|
|
|
static int apply_vma_lock_flags(unsigned long start, size_t len,
|
|
vm_flags_t flags)
|
|
{
|
|
unsigned long nstart, end, tmp;
|
|
struct vm_area_struct *vma, *prev;
|
|
int error;
|
|
|
|
VM_BUG_ON(offset_in_page(start));
|
|
VM_BUG_ON(len != PAGE_ALIGN(len));
|
|
end = start + len;
|
|
if (end < start)
|
|
return -EINVAL;
|
|
if (end == start)
|
|
return 0;
|
|
vma = find_vma(current->mm, start);
|
|
if (!vma || vma->vm_start > start)
|
|
return -ENOMEM;
|
|
|
|
prev = vma->vm_prev;
|
|
if (start > vma->vm_start)
|
|
prev = vma;
|
|
|
|
for (nstart = start ; ; ) {
|
|
vm_flags_t newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
|
|
|
|
newflags |= flags;
|
|
|
|
/* Here we know that vma->vm_start <= nstart < vma->vm_end. */
|
|
tmp = vma->vm_end;
|
|
if (tmp > end)
|
|
tmp = end;
|
|
error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
|
|
if (error)
|
|
break;
|
|
nstart = tmp;
|
|
if (nstart < prev->vm_end)
|
|
nstart = prev->vm_end;
|
|
if (nstart >= end)
|
|
break;
|
|
|
|
vma = prev->vm_next;
|
|
if (!vma || vma->vm_start != nstart) {
|
|
error = -ENOMEM;
|
|
break;
|
|
}
|
|
}
|
|
return error;
|
|
}
|
|
|
|
/*
|
|
* Go through vma areas and sum size of mlocked
|
|
* vma pages, as return value.
|
|
* Note deferred memory locking case(mlock2(,,MLOCK_ONFAULT)
|
|
* is also counted.
|
|
* Return value: previously mlocked page counts
|
|
*/
|
|
static unsigned long count_mm_mlocked_page_nr(struct mm_struct *mm,
|
|
unsigned long start, size_t len)
|
|
{
|
|
struct vm_area_struct *vma;
|
|
unsigned long count = 0;
|
|
|
|
if (mm == NULL)
|
|
mm = current->mm;
|
|
|
|
vma = find_vma(mm, start);
|
|
if (vma == NULL)
|
|
return 0;
|
|
|
|
for (; vma ; vma = vma->vm_next) {
|
|
if (start >= vma->vm_end)
|
|
continue;
|
|
if (start + len <= vma->vm_start)
|
|
break;
|
|
if (vma->vm_flags & VM_LOCKED) {
|
|
if (start > vma->vm_start)
|
|
count -= (start - vma->vm_start);
|
|
if (start + len < vma->vm_end) {
|
|
count += start + len - vma->vm_start;
|
|
break;
|
|
}
|
|
count += vma->vm_end - vma->vm_start;
|
|
}
|
|
}
|
|
|
|
return count >> PAGE_SHIFT;
|
|
}
|
|
|
|
static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t flags)
|
|
{
|
|
unsigned long locked;
|
|
unsigned long lock_limit;
|
|
int error = -ENOMEM;
|
|
|
|
start = untagged_addr(start);
|
|
|
|
if (!can_do_mlock())
|
|
return -EPERM;
|
|
|
|
len = PAGE_ALIGN(len + (offset_in_page(start)));
|
|
start &= PAGE_MASK;
|
|
|
|
lock_limit = rlimit(RLIMIT_MEMLOCK);
|
|
lock_limit >>= PAGE_SHIFT;
|
|
locked = len >> PAGE_SHIFT;
|
|
|
|
if (mmap_write_lock_killable(current->mm))
|
|
return -EINTR;
|
|
|
|
locked += current->mm->locked_vm;
|
|
if ((locked > lock_limit) && (!capable(CAP_IPC_LOCK))) {
|
|
/*
|
|
* It is possible that the regions requested intersect with
|
|
* previously mlocked areas, that part area in "mm->locked_vm"
|
|
* should not be counted to new mlock increment count. So check
|
|
* and adjust locked count if necessary.
|
|
*/
|
|
locked -= count_mm_mlocked_page_nr(current->mm,
|
|
start, len);
|
|
}
|
|
|
|
/* check against resource limits */
|
|
if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
|
|
error = apply_vma_lock_flags(start, len, flags);
|
|
|
|
mmap_write_unlock(current->mm);
|
|
if (error)
|
|
return error;
|
|
|
|
error = __mm_populate(start, len, 0);
|
|
if (error)
|
|
return __mlock_posix_error_return(error);
|
|
return 0;
|
|
}
|
|
|
|
SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
|
|
{
|
|
return do_mlock(start, len, VM_LOCKED);
|
|
}
|
|
|
|
SYSCALL_DEFINE3(mlock2, unsigned long, start, size_t, len, int, flags)
|
|
{
|
|
vm_flags_t vm_flags = VM_LOCKED;
|
|
|
|
if (flags & ~MLOCK_ONFAULT)
|
|
return -EINVAL;
|
|
|
|
if (flags & MLOCK_ONFAULT)
|
|
vm_flags |= VM_LOCKONFAULT;
|
|
|
|
return do_mlock(start, len, vm_flags);
|
|
}
|
|
|
|
SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
|
|
{
|
|
int ret;
|
|
|
|
start = untagged_addr(start);
|
|
|
|
len = PAGE_ALIGN(len + (offset_in_page(start)));
|
|
start &= PAGE_MASK;
|
|
|
|
if (mmap_write_lock_killable(current->mm))
|
|
return -EINTR;
|
|
ret = apply_vma_lock_flags(start, len, 0);
|
|
mmap_write_unlock(current->mm);
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Take the MCL_* flags passed into mlockall (or 0 if called from munlockall)
|
|
* and translate into the appropriate modifications to mm->def_flags and/or the
|
|
* flags for all current VMAs.
|
|
*
|
|
* There are a couple of subtleties with this. If mlockall() is called multiple
|
|
* times with different flags, the values do not necessarily stack. If mlockall
|
|
* is called once including the MCL_FUTURE flag and then a second time without
|
|
* it, VM_LOCKED and VM_LOCKONFAULT will be cleared from mm->def_flags.
|
|
*/
|
|
static int apply_mlockall_flags(int flags)
|
|
{
|
|
struct vm_area_struct *vma, *prev = NULL;
|
|
vm_flags_t to_add = 0;
|
|
|
|
current->mm->def_flags &= VM_LOCKED_CLEAR_MASK;
|
|
if (flags & MCL_FUTURE) {
|
|
current->mm->def_flags |= VM_LOCKED;
|
|
|
|
if (flags & MCL_ONFAULT)
|
|
current->mm->def_flags |= VM_LOCKONFAULT;
|
|
|
|
if (!(flags & MCL_CURRENT))
|
|
goto out;
|
|
}
|
|
|
|
if (flags & MCL_CURRENT) {
|
|
to_add |= VM_LOCKED;
|
|
if (flags & MCL_ONFAULT)
|
|
to_add |= VM_LOCKONFAULT;
|
|
}
|
|
|
|
for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
|
|
vm_flags_t newflags;
|
|
|
|
newflags = vma->vm_flags & VM_LOCKED_CLEAR_MASK;
|
|
newflags |= to_add;
|
|
|
|
/* Ignore errors */
|
|
mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
|
|
cond_resched();
|
|
}
|
|
out:
|
|
return 0;
|
|
}
|
|
|
|
SYSCALL_DEFINE1(mlockall, int, flags)
|
|
{
|
|
unsigned long lock_limit;
|
|
int ret;
|
|
|
|
if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE | MCL_ONFAULT)) ||
|
|
flags == MCL_ONFAULT)
|
|
return -EINVAL;
|
|
|
|
if (!can_do_mlock())
|
|
return -EPERM;
|
|
|
|
lock_limit = rlimit(RLIMIT_MEMLOCK);
|
|
lock_limit >>= PAGE_SHIFT;
|
|
|
|
if (mmap_write_lock_killable(current->mm))
|
|
return -EINTR;
|
|
|
|
ret = -ENOMEM;
|
|
if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
|
|
capable(CAP_IPC_LOCK))
|
|
ret = apply_mlockall_flags(flags);
|
|
mmap_write_unlock(current->mm);
|
|
if (!ret && (flags & MCL_CURRENT))
|
|
mm_populate(0, TASK_SIZE);
|
|
|
|
return ret;
|
|
}
|
|
|
|
SYSCALL_DEFINE0(munlockall)
|
|
{
|
|
int ret;
|
|
|
|
if (mmap_write_lock_killable(current->mm))
|
|
return -EINTR;
|
|
ret = apply_mlockall_flags(0);
|
|
mmap_write_unlock(current->mm);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
|
|
* shm segments) get accounted against the user_struct instead.
|
|
*/
|
|
static DEFINE_SPINLOCK(shmlock_user_lock);
|
|
|
|
int user_shm_lock(size_t size, struct ucounts *ucounts)
|
|
{
|
|
unsigned long lock_limit, locked;
|
|
long memlock;
|
|
int allowed = 0;
|
|
|
|
locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
|
|
lock_limit = rlimit(RLIMIT_MEMLOCK);
|
|
if (lock_limit == RLIM_INFINITY)
|
|
allowed = 1;
|
|
lock_limit >>= PAGE_SHIFT;
|
|
spin_lock(&shmlock_user_lock);
|
|
memlock = inc_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, locked);
|
|
|
|
if (!allowed && (memlock == LONG_MAX || memlock > lock_limit) && !capable(CAP_IPC_LOCK)) {
|
|
dec_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, locked);
|
|
goto out;
|
|
}
|
|
if (!get_ucounts(ucounts)) {
|
|
dec_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, locked);
|
|
goto out;
|
|
}
|
|
allowed = 1;
|
|
out:
|
|
spin_unlock(&shmlock_user_lock);
|
|
return allowed;
|
|
}
|
|
|
|
void user_shm_unlock(size_t size, struct ucounts *ucounts)
|
|
{
|
|
spin_lock(&shmlock_user_lock);
|
|
dec_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, (size + PAGE_SIZE - 1) >> PAGE_SHIFT);
|
|
spin_unlock(&shmlock_user_lock);
|
|
put_ucounts(ucounts);
|
|
}
|