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![Sergei Trofimovich](/assets/img/avatar_default.png)
When page_poison detects page corruption it's useful to see who freed a page recently to have a guess where write-after-free corruption happens. After this change corruption report has extra page data. Example report from real corruption (includes only page_pwner part): pagealloc: memory corruption e00000014cd61d10: 11 00 00 00 00 00 00 00 30 1d d2 ff ff 0f 00 60 ........0......` e00000014cd61d20: b0 1d d2 ff ff 0f 00 60 90 fe 1c 00 08 00 00 20 .......`....... ... CPU: 1 PID: 220402 Comm: cc1plus Not tainted 5.12.0-rc5-00107-g9720c6f59ecf #245 Hardware name: hp server rx3600, BIOS 04.03 04/08/2008 ... Call Trace: [<a000000100015210>] show_stack+0x90/0xc0 [<a000000101163390>] dump_stack+0x150/0x1c0 [<a0000001003f1e90>] __kernel_unpoison_pages+0x410/0x440 [<a0000001003c2460>] get_page_from_freelist+0x1460/0x2ca0 [<a0000001003c6be0>] __alloc_pages_nodemask+0x3c0/0x660 [<a0000001003ed690>] alloc_pages_vma+0xb0/0x500 [<a00000010037deb0>] __handle_mm_fault+0x1230/0x1fe0 [<a00000010037ef70>] handle_mm_fault+0x310/0x4e0 [<a00000010005dc70>] ia64_do_page_fault+0x1f0/0xb80 [<a00000010000ca00>] ia64_leave_kernel+0x0/0x270 page_owner tracks the page as freed page allocated via order 0, migratetype Movable, gfp_mask 0x100dca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO), pid 37, ts 8173444098740 __reset_page_owner+0x40/0x200 free_pcp_prepare+0x4d0/0x600 free_unref_page+0x20/0x1c0 __put_page+0x110/0x1a0 migrate_pages+0x16d0/0x1dc0 compact_zone+0xfc0/0x1aa0 proactive_compact_node+0xd0/0x1e0 kcompactd+0x550/0x600 kthread+0x2c0/0x2e0 call_payload+0x50/0x80 Here we can see that page was freed by page migration but something managed to write to it afterwards. [slyfox@gentoo.org: s/dump_page_owner/dump_page/, per Vlastimil] Link: https://lkml.kernel.org/r/20210407230800.1086854-1-slyfox@gentoo.org Link: https://lkml.kernel.org/r/20210404141735.2152984-1-slyfox@gentoo.org Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org> Acked-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
106 lines
2.5 KiB
C
106 lines
2.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/kernel.h>
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#include <linux/string.h>
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#include <linux/mm.h>
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#include <linux/mmdebug.h>
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#include <linux/highmem.h>
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#include <linux/page_ext.h>
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#include <linux/poison.h>
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#include <linux/ratelimit.h>
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#include <linux/kasan.h>
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bool _page_poisoning_enabled_early;
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EXPORT_SYMBOL(_page_poisoning_enabled_early);
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DEFINE_STATIC_KEY_FALSE(_page_poisoning_enabled);
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EXPORT_SYMBOL(_page_poisoning_enabled);
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static int __init early_page_poison_param(char *buf)
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{
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return kstrtobool(buf, &_page_poisoning_enabled_early);
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}
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early_param("page_poison", early_page_poison_param);
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static void poison_page(struct page *page)
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{
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void *addr = kmap_atomic(page);
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/* KASAN still think the page is in-use, so skip it. */
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kasan_disable_current();
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memset(kasan_reset_tag(addr), PAGE_POISON, PAGE_SIZE);
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kasan_enable_current();
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kunmap_atomic(addr);
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}
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void __kernel_poison_pages(struct page *page, int n)
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{
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int i;
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for (i = 0; i < n; i++)
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poison_page(page + i);
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}
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static bool single_bit_flip(unsigned char a, unsigned char b)
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{
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unsigned char error = a ^ b;
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return error && !(error & (error - 1));
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}
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static void check_poison_mem(struct page *page, unsigned char *mem, size_t bytes)
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{
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static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
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unsigned char *start;
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unsigned char *end;
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start = memchr_inv(mem, PAGE_POISON, bytes);
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if (!start)
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return;
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for (end = mem + bytes - 1; end > start; end--) {
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if (*end != PAGE_POISON)
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break;
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}
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if (!__ratelimit(&ratelimit))
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return;
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else if (start == end && single_bit_flip(*start, PAGE_POISON))
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pr_err("pagealloc: single bit error\n");
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else
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pr_err("pagealloc: memory corruption\n");
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print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
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end - start + 1, 1);
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dump_stack();
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dump_page(page, "pagealloc: corrupted page details");
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}
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static void unpoison_page(struct page *page)
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{
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void *addr;
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addr = kmap_atomic(page);
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kasan_disable_current();
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/*
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* Page poisoning when enabled poisons each and every page
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* that is freed to buddy. Thus no extra check is done to
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* see if a page was poisoned.
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*/
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check_poison_mem(page, kasan_reset_tag(addr), PAGE_SIZE);
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kasan_enable_current();
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kunmap_atomic(addr);
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}
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void __kernel_unpoison_pages(struct page *page, int n)
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{
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int i;
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for (i = 0; i < n; i++)
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unpoison_page(page + i);
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}
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#ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC
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void __kernel_map_pages(struct page *page, int numpages, int enable)
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{
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/* This function does nothing, all work is done via poison pages */
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}
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#endif
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