6.6-stable review patch. If anyone has any objections, please let me know.
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From: Brian Johannesmeyer bjohannesmeyer@gmail.com
[ 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@gmail.com Signed-off-by: Borislav Petkov (AMD) bp@alien8.de Reviewed-by: Alexander Potapenko glider@google.com Link: https://lore.kernel.org/r/20240523215029.4160518-1-bjohannesmeyer@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/lib/iomem.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
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)