The patch titled
Subject: mm: prevent page_frag_alloc() from corrupting the memory
has been added to the -mm mm-unstable branch. Its filename is
mm-prevent-page_frag_alloc-from-corrupting-the-memory.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-prevent-page_frag_alloc-from-corrupting-the-memory.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Maurizio Lombardi <mlombard@xxxxxxxxxx>
Subject: mm: prevent page_frag_alloc() from corrupting the memory
Date: Fri, 15 Jul 2022 14:50:13 +0200
A number of drivers call page_frag_alloc() with a fragment's size >
PAGE_SIZE.
In low memory conditions, __page_frag_cache_refill() may fail the order
3 cache allocation and fall back to order 0; In this case, the cache
will be smaller than the fragment, causing memory corruptions.
Prevent this from happening by checking if the newly allocated cache is
large enough for the fragment; if not, the allocation will fail and
page_frag_alloc() will return NULL.
Link: https://lkml.kernel.org/r/20220715125013.247085-1-mlombard@xxxxxxxxxx
Signed-off-by: Maurizio Lombardi <mlombard@xxxxxxxxxx>
Reviewed-by: Alexander Duyck <alexanderduyck@xxxxxx>
Cc: Chen Lin <chen45464546@xxxxxxx>
Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
--- a/mm/page_alloc.c~mm-prevent-page_frag_alloc-from-corrupting-the-memory
+++ a/mm/page_alloc.c
@@ -5697,6 +5697,18 @@ refill:
/* reset page count bias and offset to start of new frag */
nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1;
offset = size - fragsz;
+ if (unlikely(offset < 0)) {
+ /*
+ * The caller is trying to allocate a fragment
+ * with fragsz > PAGE_SIZE but the cache isn't big
+ * enough to satisfy the request, this may
+ * happen in low memory conditions.
+ * We don't release the cache page because
+ * it could make memory pressure worse
+ * so we simply return NULL here.
+ */
+ return NULL;
+ }
}
nc->pagecnt_bias--;
_
Patches currently in -mm which might be from mlombard@xxxxxxxxxx are
mm-prevent-page_frag_alloc-from-corrupting-the-memory.patch
