This is a note to let you know that I've just added the patch titled
x86/kmsan: Fix hook for unaligned accesses
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-kmsan-fix-hook-for-unaligned-accesses.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 68d30d27b4f66ef79d5d9861bba086ed007c74ed
Author: Brian Johannesmeyer <bjohannesmeyer@xxxxxxxxx>
Date: Thu May 23 23:50:29 2024 +0200
x86/kmsan: Fix hook for unaligned accesses
[ Upstream commit bf6ab33d8487f5e2a0998ce75286eae65bb0a6d6 ]
When called with a 'from' that is not 4-byte-aligned, string_memcpy_fromio()
calls the movs() macro to copy the first few bytes, so that 'from' becomes
4-byte-aligned before calling rep_movs(). This movs() macro modifies 'to', and
the subsequent line modifies 'n'.
As a result, on unaligned accesses, kmsan_unpoison_memory() uses the updated
(aligned) values of 'to' and 'n'. Hence, it does not unpoison the entire
region.
Save the original values of 'to' and 'n', and pass those to
kmsan_unpoison_memory(), so that the entire region is unpoisoned.
Signed-off-by: Brian Johannesmeyer <bjohannesmeyer@xxxxxxxxx>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240523215029.4160518-1-bjohannesmeyer@xxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/x86/lib/iomem.c b/arch/x86/lib/iomem.c
index e0411a3774d4..5eecb45d05d5 100644
--- a/arch/x86/lib/iomem.c
+++ b/arch/x86/lib/iomem.c
@@ -25,6 +25,9 @@ static __always_inline void rep_movs(void *to, const void *from, size_t n)
static void string_memcpy_fromio(void *to, const volatile void __iomem *from, size_t n)
{
+ const void *orig_to = to;
+ const size_t orig_n = n;
+
if (unlikely(!n))
return;
@@ -39,7 +42,7 @@ static void string_memcpy_fromio(void *to, const volatile void __iomem *from, si
}
rep_movs(to, (const void *)from, n);
/* KMSAN must treat values read from devices as initialized. */
- kmsan_unpoison_memory(to, n);
+ kmsan_unpoison_memory(orig_to, orig_n);
}
static void string_memcpy_toio(volatile void __iomem *to, const void *from, size_t n)
