RE: [PATCH] mm: kfence: Fix false positives on big endian
From: David Laight <hidden>
Date: 2023-05-05 16:02:27
Also in:
linux-mm, lkml
From: Michael Ellerman
quoted hunk ↗ jump to hunk
Sent: 05 May 2023 04:51 Since commit 1ba3cbf3ec3b ("mm: kfence: improve the performance of __kfence_alloc() and __kfence_free()"), kfence reports failures in random places at boot on big endian machines. The problem is that the new KFENCE_CANARY_PATTERN_U64 encodes the address of each byte in its value, so it needs to be byte swapped on big endian machines. The compiler is smart enough to do the le64_to_cpu() at compile time, so there is no runtime overhead. Fixes: 1ba3cbf3ec3b ("mm: kfence: improve the performance of __kfence_alloc() and __kfence_free()") Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> --- mm/kfence/kfence.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/mm/kfence/kfence.h b/mm/kfence/kfence.h index 2aafc46a4aaf..392fb273e7bd 100644 --- a/mm/kfence/kfence.h +++ b/mm/kfence/kfence.h@@ -29,7 +29,7 @@ * canary of every 8 bytes is the same. 64-bit memory can be filled and checked * at a time instead of byte by byte to improve performance. */ -#define KFENCE_CANARY_PATTERN_U64 ((u64)0xaaaaaaaaaaaaaaaa ^ (u64)(0x0706050403020100)) +#define KFENCE_CANARY_PATTERN_U64 ((u64)0xaaaaaaaaaaaaaaaa ^ (u64)(le64_to_cpu(0x0706050403020100)))
What at the (u64) casts for? The constants should probably have a ul (or ull) suffix. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)