Commit 7976c149 authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Herbert Xu
Browse files

crypto: crypto_xor - use helpers for unaligned accesses 



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: default avatarArd Biesheuvel <ardb@kernel.org>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent 4920a4a7

crypto/algapi.c

+21 −3
Original line number Diff line number Diff line
@@ -1022,7 +1022,13 @@ void __crypto_xor(u8 *dst, const u8 *src1, const u8 *src2, unsigned int len) 
	}



	while (IS_ENABLED(CONFIG_64BIT) && len >= 8 && !(relalign & 7)) {

		if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) {

			u64 l = get_unaligned((u64 *)src1) ^

				get_unaligned((u64 *)src2);

			put_unaligned(l, (u64 *)dst);

		} else {

			*(u64 *)dst = *(u64 *)src1 ^ *(u64 *)src2;

		}

		dst += 8;

		src1 += 8;

		src2 += 8;
@@ -1030,7 +1036,13 @@ void __crypto_xor(u8 *dst, const u8 *src1, const u8 *src2, unsigned int len) 
	}



	while (len >= 4 && !(relalign & 3)) {

		if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) {

			u32 l = get_unaligned((u32 *)src1) ^

				get_unaligned((u32 *)src2);

			put_unaligned(l, (u32 *)dst);

		} else {

			*(u32 *)dst = *(u32 *)src1 ^ *(u32 *)src2;

		}

		dst += 4;

		src1 += 4;

		src2 += 4;
@@ -1038,7 +1050,13 @@ void __crypto_xor(u8 *dst, const u8 *src1, const u8 *src2, unsigned int len) 
	}



	while (len >= 2 && !(relalign & 1)) {

		if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) {

			u16 l = get_unaligned((u16 *)src1) ^

				get_unaligned((u16 *)src2);

			put_unaligned(l, (u16 *)dst);

		} else {

			*(u16 *)dst = *(u16 *)src1 ^ *(u16 *)src2;

		}

		dst += 2;

		src1 += 2;

		src2 += 2;

include/crypto/algapi.h

+8 −2
Original line number Diff line number Diff line
@@ -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 {