From f58bd538e6a2deb2bcdfe527d9ed45643348a4e6 Mon Sep 17 00:00:00 2001 From: Sergei Trofimovich Date: Thu, 29 Apr 2021 22:55:12 -0700 Subject: mm: page_poison: print page info when corruption is caught 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: [] show_stack+0x90/0xc0 [] dump_stack+0x150/0x1c0 [] __kernel_unpoison_pages+0x410/0x440 [] get_page_from_freelist+0x1460/0x2ca0 [] __alloc_pages_nodemask+0x3c0/0x660 [] alloc_pages_vma+0xb0/0x500 [] __handle_mm_fault+0x1230/0x1fe0 [] handle_mm_fault+0x310/0x4e0 [] ia64_do_page_fault+0x1f0/0xb80 [] 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 Acked-by: Vlastimil Babka Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page_poison.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/mm/page_poison.c b/mm/page_poison.c index 655dc5895604..98438985e1ed 100644 --- a/mm/page_poison.c +++ b/mm/page_poison.c @@ -2,6 +2,7 @@ #include #include #include +#include #include #include #include @@ -45,7 +46,7 @@ static bool single_bit_flip(unsigned char a, unsigned char b) return error && !(error & (error - 1)); } -static void check_poison_mem(unsigned char *mem, size_t bytes) +static void check_poison_mem(struct page *page, unsigned char *mem, size_t bytes) { static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10); unsigned char *start; @@ -70,6 +71,7 @@ static void check_poison_mem(unsigned char *mem, size_t bytes) print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start, end - start + 1, 1); dump_stack(); + dump_page(page, "pagealloc: corrupted page details"); } static void unpoison_page(struct page *page) @@ -83,7 +85,7 @@ static void unpoison_page(struct page *page) * that is freed to buddy. Thus no extra check is done to * see if a page was poisoned. */ - check_poison_mem(kasan_reset_tag(addr), PAGE_SIZE); + check_poison_mem(page, kasan_reset_tag(addr), PAGE_SIZE); kasan_enable_current(); kunmap_atomic(addr); } -- cgit