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Thu, 13 Nov 2025 18:54:52 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id K7EKDHwpFml8JwAAD6G6ig (envelope-from ); Thu, 13 Nov 2025 18:54:52 +0000 From: Vlastimil Babka Date: Thu, 13 Nov 2025 19:54:35 +0100 Subject: [PATCH] mm/mempool: fix poisoning order>0 pages with HIGHMEM Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20251113-mempool-poison-v1-1-233b3ef984c3@suse.cz> X-B4-Tracking: v=1; b=H4sIAGopFmkC/x3MQQqAIBBA0avErBMaK6iuEi0spxpIRxQiCO+et HyL/19IFJkSTNULkW5OLL4A6wq20/iDFNti0I3uEbFVjlwQuVQQTuLV1gxoBr2Otu+gRCHSzs8 /nJecP93ZIEZgAAAA X-Change-ID: 20251113-mempool-poison-c081a82b9d54 To: Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo Cc: Jens Axboe , linux-block@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel test robot , Christoph Hellwig , Vlastimil Babka X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; 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NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RCVD_VIA_SMTP_AUTH(0.00)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; ARC_NA(0.00)[]; RCPT_COUNT_TWELVE(0.00)[12]; MIME_TRACE(0.00)[0:+]; RCVD_TLS_ALL(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; DBL_BLOCKED_OPENRESOLVER(0.00)[intel.com:email]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DKIM_TRACE(0.00)[suse.cz:+] X-Spam-Score: -4.51 The kernel test has reported: BUG: unable to handle page fault for address: fffba000 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page *pde =3D 03171067 *pte =3D 00000000 Oops: Oops: 0002 [#1] CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Tainted: G T 6.18.0= -rc2-00031-gec7f31b2a2d3 #1 NONE a1d066dfe789f54bc7645c7989957d2bdee593ca Tainted: [T]=3DRANDSTRUCT Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian= -1.16.3-2 04/01/2014 EIP: memset (arch/x86/include/asm/string_32.h:168 arch/x86/lib/memcpy_32.= c:17) Code: a5 8b 4d f4 83 e1 03 74 02 f3 a4 83 c4 04 5e 5f 5d 2e e9 73 41 01 0= 0 90 90 90 3e 8d 74 26 00 55 89 e5 57 56 89 c6 89 d0 89 f7 aa 89 f0 5e= 5f 5d 2e e9 53 41 01 00 cc cc cc 55 89 e5 53 57 56 EAX: 0000006b EBX: 00000015 ECX: 001fefff EDX: 0000006b ESI: fffb9000 EDI: fffba000 EBP: c611fbf0 ESP: c611fbe8 DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068 EFLAGS: 00010287 CR0: 80050033 CR2: fffba000 CR3: 0316e000 CR4: 00040690 Call Trace: poison_element (mm/mempool.c:83 mm/mempool.c:102) mempool_init_node (mm/mempool.c:142 mm/mempool.c:226) mempool_init_noprof (mm/mempool.c:250 (discriminator 1)) ? mempool_alloc_pages (mm/mempool.c:640) bio_integrity_initfn (block/bio-integrity.c:483 (discriminator 8)) ? mempool_alloc_pages (mm/mempool.c:640) do_one_initcall (init/main.c:1283) Christoph found out this is due to the poisoning code not dealing properly with CONFIG_HIGHMEM because only the first page is mapped but then the whole potentially high-order page is accessed. This went unnoticed for years probably because nobody has yet used a mempool for order>0 pages before the new block code in -next. We could give up on HIGHMEM here, but it's straightforward to fix this with a loop that's mapping, poisoning or checking and unmapping individual pages. Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-lkp/202511111411.9ebfa1ba-lkp@intel.com Analyzed-by: Christoph Hellwig Fixes: bdfedb76f4f5 ("mm, mempool: poison elements backed by slab allocator= ") Tested-by: kernel test robot Signed-off-by: Vlastimil Babka Reviewed-by: Christoph Hellwig --- Will push to slab/for-next-fixes=20 --- mm/mempool.c | 32 ++++++++++++++++++++++++++------ 1 file changed, 26 insertions(+), 6 deletions(-) diff --git a/mm/mempool.c b/mm/mempool.c index 1c38e873e546..d7bbf1189db9 100644 --- a/mm/mempool.c +++ b/mm/mempool.c @@ -68,10 +68,20 @@ static void check_element(mempool_t *pool, void *elemen= t) } else if (pool->free =3D=3D mempool_free_pages) { /* Mempools backed by page allocator */ int order =3D (int)(long)pool->pool_data; - void *addr =3D kmap_local_page((struct page *)element); =20 - __check_element(pool, addr, 1UL << (PAGE_SHIFT + order)); - kunmap_local(addr); +#ifdef CONFIG_HIGHMEM + for (int i =3D 0; i < (1 << order); i++) { + struct page *page =3D (struct page *)element; + void *addr =3D kmap_local_page(page + i); + + __check_element(pool, addr, PAGE_SIZE); + kunmap_local(addr); + } +#else + void *addr =3D page_address((struct page *)element); + + __check_element(pool, addr, PAGE_SIZE << order); +#endif } } =20 @@ -97,10 +107,20 @@ static void poison_element(mempool_t *pool, void *elem= ent) } else if (pool->alloc =3D=3D mempool_alloc_pages) { /* Mempools backed by page allocator */ int order =3D (int)(long)pool->pool_data; - void *addr =3D kmap_local_page((struct page *)element); =20 - __poison_element(addr, 1UL << (PAGE_SHIFT + order)); - kunmap_local(addr); +#ifdef CONFIG_HIGHMEM + for (int i =3D 0; i < (1 << order); i++) { + struct page *page =3D (struct page *)element; + void *addr =3D kmap_local_page(page + i); + + __poison_element(addr, PAGE_SIZE); + kunmap_local(addr); + } +#else + void *addr =3D page_address((struct page *)element); + + __poison_element(addr, PAGE_SIZE << order); +#endif } } #else /* CONFIG_SLUB_DEBUG_ON */ --- base-commit: e9a6fb0bcdd7609be6969112f3fbfcce3b1d4a7c change-id: 20251113-mempool-poison-c081a82b9d54 Best regards, --=20 Vlastimil Babka