FAILED: patch "[PATCH] mm/mempool: fix poisoning order>0 pages with HIGHMEM" failed to apply to 6.6-stable tree

PATCH New [email protected] 2 participants 3 messages Nov 24, 2025

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Stable branch Memory management Slab allocator

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[email protected]

author maintainer

2025-11-24 13:36 UTC #0 lore raw

The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x ec33b59542d96830e3c89845ff833cf7b25ef172
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025112434-uncle-ethics-cb16@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From ec33b59542d96830e3c89845ff833cf7b25ef172 Mon Sep 17 00:00:00 2001
From: Vlastimil Babka <[email protected]>
Date: Thu, 13 Nov 2025 19:54:35 +0100
Subject: [PATCH] mm/mempool: fix poisoning order>0 pages with HIGHMEM

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 = 03171067 *pte = 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]=RANDSTRUCT
  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 00 90 90 90 3e 8d 74 26 00 55 89 e5 57 56 89 c6 89 d0 89 f7 <f3> 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.

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 <[email protected]>

Closes https://lore.kernel.org/oe-lkp/[email protected] open here

Analyzed-by Christoph Hellwig <[email protected]>

Fixes bdfedb76f4f5 ("mm, mempool: poison elements backed by slab allocator")

Cc [email protected]

Tested-by kernel test robot <[email protected]>

Reviewed-by Christoph Hellwig <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Vlastimil Babka <[email protected]>

mm/mempool.c +26 -6

index 1c38e873e546..d7bbf1189db9 100644
@@ -68,10 +68,20 @@ static void check_element(mempool_t *pool, void *element)
 	} else if (pool->free == mempool_free_pages) {
 		/* Mempools backed by page allocator */
 		int order = (int)(long)pool->pool_data;
-		void *addr = kmap_local_page((struct page *)element);
 
-		__check_element(pool, addr, 1UL << (PAGE_SHIFT + order));
-		kunmap_local(addr);
+#ifdef CONFIG_HIGHMEM
+		for (int i = 0; i < (1 << order); i++) {
+			struct page *page = (struct page *)element;
+			void *addr = kmap_local_page(page + i);
+
+			__check_element(pool, addr, PAGE_SIZE);
+			kunmap_local(addr);
+		}
+#else
+		void *addr = page_address((struct page *)element);
+
+		__check_element(pool, addr, PAGE_SIZE << order);
+#endif
 	}
 }

@@ -97,10 +107,20 @@ static void poison_element(mempool_t *pool, void *element)
 	} else if (pool->alloc == mempool_alloc_pages) {
 		/* Mempools backed by page allocator */
 		int order = (int)(long)pool->pool_data;
-		void *addr = kmap_local_page((struct page *)element);
 
-		__poison_element(addr, 1UL << (PAGE_SHIFT + order));
-		kunmap_local(addr);
+#ifdef CONFIG_HIGHMEM
+		for (int i = 0; i < (1 << order); i++) {
+			struct page *page = (struct page *)element;
+			void *addr = kmap_local_page(page + i);
+
+			__poison_element(addr, PAGE_SIZE);
+			kunmap_local(addr);
+		}
+#else
+		void *addr = page_address((struct page *)element);
+
+		__poison_element(addr, PAGE_SIZE << order);
+#endif
 	}
 }
 #else /* CONFIG_SLUB_DEBUG_ON */

Sasha Levin

maintainer

2025-11-24 20:59 UTC #1 lore raw

PATCH 1/2 mm/mempool: replace kmap_atomic() with kmap_local_page()

From: "Fabio M. De Francesco" <[email protected]>

[ Upstream commit f2bcc99a5e901a13b754648d1dbab60f4adf9375 ]

kmap_atomic() has been deprecated in favor of kmap_local_page().

Therefore, replace kmap_atomic() with kmap_local_page().

kmap_atomic() is implemented like a kmap_local_page() which also disables page-faults and preemption (the latter only in !PREEMPT_RT kernels). The kernel virtual addresses returned by these two API are only valid in the context of the callers (i.e., they cannot be handed to other threads).

With kmap_local_page() the mappings are per thread and CPU local like in kmap_atomic(); however, they can handle page-faults and can be called from any context (including interrupts). The tasks that call kmap_local_page() can be preempted and, when they are scheduled to run again, the kernel virtual addresses are restored and are still valid.

The code blocks between the mappings and un-mappings don't rely on the above-mentioned side effects of kmap_atomic(), so that mere replacements of the old API with the new one is all that they require (i.e., there is no need to explicitly call pagefault_disable() and/or preempt_disable()).

Link https://lkml.kernel.org/r/[email protected] open here

Signed-off-by Fabio M. De Francesco <[email protected]>

Cc Ira Weiny <[email protected]>

Signed-off-by Andrew Morton <[email protected]>

Stable-dep-of: ec33b59542d9 ("mm/mempool: fix poisoning order>0 pages with HIGHMEM")

Signed-off-by Sasha Levin <[email protected]>

---
 mm/mempool.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

mm/mempool.c +4 -4

index 734bcf5afbb78..b3d2084fd989c 100644
@@ -64,10 +64,10 @@ static void check_element(mempool_t *pool, void *element)
 	} else if (pool->free == mempool_free_pages) {
 		/* Mempools backed by page allocator */
 		int order = (int)(long)pool->pool_data;
-		void *addr = kmap_atomic((struct page *)element);
+		void *addr = kmap_local_page((struct page *)element);
 
 		__check_element(pool, addr, 1UL << (PAGE_SHIFT + order));
-		kunmap_atomic(addr);
+		kunmap_local(addr);
 	}
 }

@@ -89,10 +89,10 @@ static void poison_element(mempool_t *pool, void *element)
 	} else if (pool->alloc == mempool_alloc_pages) {
 		/* Mempools backed by page allocator */
 		int order = (int)(long)pool->pool_data;
-		void *addr = kmap_atomic((struct page *)element);
+		void *addr = kmap_local_page((struct page *)element);
 
 		__poison_element(addr, 1UL << (PAGE_SHIFT + order));
-		kunmap_atomic(addr);
+		kunmap_local(addr);
 	}
 }
 #else /* CONFIG_DEBUG_SLAB || CONFIG_SLUB_DEBUG_ON */

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