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Wed, 7 Apr 2021 12:15:50 +0000 (UTC) Subject: Re: [PATCH] mm: page_poison: print page owner info when corruption is caught To: Sergei Trofimovich , Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20210404141735.2152984-1-slyfox@gentoo.org> From: Vlastimil Babka Message-ID: <2f0d1127-8868-f8a3-203f-2c3d473bd496@suse.cz> Date: Wed, 7 Apr 2021 14:15:50 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210404141735.2152984-1-slyfox@gentoo.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 8DB2C40002D8 X-Stat-Signature: z7kbpuynmq43u1zot5qgbbubtni77job Received-SPF: none (suse.cz>: No applicable sender policy available) receiver=imf17; identity=mailfrom; envelope-from=""; helo=mx2.suse.de; client-ip=195.135.220.15 X-HE-DKIM-Result: none/none X-HE-Tag: 1617797750-274094 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 4/4/21 4:17 PM, Sergei Trofimovich wrote: > 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_owner data. > Example report from real corruption: > > pagealloc: memory corruption > e00000014cd61d10: 11 00 00 00 00 00 00 00 30 1d d2 ff ff 0f 00 60 > 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. > > CC: Andrew Morton > CC: linux-mm@kvack.org > Signed-off-by: Sergei Trofimovich > --- > 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 65cdf844c8ad..ef2a1eab13d7 100644 > --- a/mm/page_poison.c > +++ b/mm/page_poison.c > @@ -4,6 +4,7 @@ > #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_owner(page); OK but why not a full dump_page()? > } > > static void unpoison_page(struct page *page) > @@ -82,7 +84,7 @@ 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(addr, PAGE_SIZE); > + check_poison_mem(page, addr, PAGE_SIZE); > kunmap_atomic(addr); > } > >