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crypto: crypto_xor - use helpers for unaligned accesses

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Dereferencing a misaligned pointer is undefined behavior in C, and may
result in codegen on architectures such as ARM that trigger alignments
traps and expensive fixups in software.

Instead, use the get_aligned()/put_aligned() accessors, which are cheap
or even completely free when CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y.

In the converse case, the prior alignment checks ensure that the casts
are safe, and so no unaligned accessors are necessary.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Ard Biesheuvel
2022-02-23 08:07:01 +01:00
committed by Herbert Xu
parent 4920a4a726
commit 7976c14925
2 changed files with 29 additions and 5 deletions
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10
include/crypto/algapi.h
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@@ -13,6 +13,8 @@
#include <linux/list.h>
#include <linux/types.h>
#include <asm/unaligned.h>
/*
* Maximum values for blocksize and alignmask, used to allocate
* static buffers that are big enough for any combination of
@@ -154,9 +156,11 @@ static inline void crypto_xor(u8 *dst, const u8 *src, unsigned int size)
(size % sizeof(unsigned long)) == 0) {
unsigned long *d = (unsigned long *)dst;
unsigned long *s = (unsigned long *)src;
unsigned long l;
while (size > 0) {
*d++ ^= *s++;
l = get_unaligned(d) ^ get_unaligned(s++);
put_unaligned(l, d++);
size -= sizeof(unsigned long);
}
} else {
@@ -173,9 +177,11 @@ static inline void crypto_xor_cpy(u8 *dst, const u8 *src1, const u8 *src2,
unsigned long *d = (unsigned long *)dst;
unsigned long *s1 = (unsigned long *)src1;
unsigned long *s2 = (unsigned long *)src2;
unsigned long l;
while (size > 0) {
*d++ = *s1++ ^ *s2++;
l = get_unaligned(s1++) ^ get_unaligned(s2++);
put_unaligned(l, d++);
size -= sizeof(unsigned long);
}
} else {