From cd5528621abb01664a477392cd3e76be2ef6296b Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Sun, 2 Nov 2025 15:42:08 -0800 Subject: [PATCH] lib/crypto: x86/blake2s: Avoid writing back unchanged 'f' value Just before returning, blake2s_compress_ssse3() and blake2s_compress_avx512() store updated values to the 'h', 't', and 'f' fields of struct blake2s_ctx. But 'f' is always unchanged (which is correct; only the C code changes it). So, there's no need to write to 'f'. Use 64-bit stores (movq and vmovq) instead of 128-bit stores (movdqu and vmovdqu) so that only 't' is written. Reviewed-by: Ard Biesheuvel Link: https://lore.kernel.org/r/20251102234209.62133-6-ebiggers@kernel.org Signed-off-by: Eric Biggers --- lib/crypto/x86/blake2s-core.S | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/lib/crypto/x86/blake2s-core.S b/lib/crypto/x86/blake2s-core.S index f805a49c590d5..869064f6ac16e 100644 --- a/lib/crypto/x86/blake2s-core.S +++ b/lib/crypto/x86/blake2s-core.S @@ -193,7 +193,7 @@ SYM_FUNC_START(blake2s_compress_ssse3) movdqu %xmm0,(CTX) // Store new h[0..3] movdqu %xmm1,16(CTX) // Store new h[4..7] - movdqu %xmm14,32(CTX) // Store new t and f + movq %xmm14,32(CTX) // Store new t (f is unchanged) RET SYM_FUNC_END(blake2s_compress_ssse3) @@ -287,7 +287,7 @@ SYM_FUNC_START(blake2s_compress_avx512) vmovdqu %xmm0,(CTX) // Store new h[0..3] vmovdqu %xmm1,16(CTX) // Store new h[4..7] - vmovdqu %xmm4,32(CTX) // Store new t and f + vmovq %xmm4,32(CTX) // Store new t (f is unchanged) vzeroupper RET SYM_FUNC_END(blake2s_compress_avx512) -- 2.47.3