Commit eec76ea5 authored by Eric Biggers's avatar Eric Biggers
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lib/crypto: arm64/poly1305: Fix register corruption in no-SIMD contexts 



Restore the SIMD usability check that was removed by commit a59e5468
("crypto: arm64/poly1305 - Add block-only interface").

This safety check is cheap and is well worth eliminating a footgun.
While the Poly1305 functions should not be called when SIMD registers
are unusable, if they are anyway, they should just do the right thing
instead of corrupting random tasks' registers and/or computing incorrect
MACs.  Fixing this is also needed for poly1305_kunit to pass.

Just use may_use_simd() instead of the original crypto_simd_usable(),
since poly1305_kunit won't rely on crypto_simd_disabled_for_test.

Fixes: a59e5468 ("crypto: arm64/poly1305 - Add block-only interface")
Cc: stable@vger.kernel.org
Reviewed-by: default avatarArd Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250706231100.176113-4-ebiggers@kernel.org


Signed-off-by: default avatarEric Biggers <ebiggers@kernel.org>
parent 52c3e242

lib/crypto/arm64/poly1305-glue.c

+2 −1
Original line number Diff line number Diff line
@@ -7,6 +7,7 @@ 


#include <asm/hwcap.h>

#include <asm/neon.h>

#include <asm/simd.h>

#include <crypto/internal/poly1305.h>

#include <linux/cpufeature.h>

#include <linux/jump_label.h>
@@ -33,7 +34,7 @@ void poly1305_blocks_arch(struct poly1305_block_state *state, const u8 *src, 
			  unsigned int len, u32 padbit)

{

	len = round_down(len, POLY1305_BLOCK_SIZE);

	if (static_branch_likely(&have_neon)) {

	if (static_branch_likely(&have_neon) && likely(may_use_simd())) {

		do {

			unsigned int todo = min_t(unsigned int, len, SZ_4K);