linux-kernel - [PATCH] crypto: x86/aes-gcm-vaes-avx2 - initialize full %rax return register

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Message-ID: <20251102015256.171536-1-ebiggers@kernel.org>
Date: Sat,  1 Nov 2025 18:52:56 -0700
From: Eric Biggers <ebiggers@...nel.org>
To: linux-crypto@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	Ard Biesheuvel <ardb@...nel.org>,
	"Jason A . Donenfeld" <Jason@...c4.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Eric Biggers <ebiggers@...nel.org>
Subject: [PATCH] crypto: x86/aes-gcm-vaes-avx2 - initialize full %rax return register

Update aes_gcm_dec_final_vaes_avx2() to be consistent with
aes_gcm_dec_final_aesni() and aes_gcm_dec_final_vaes_avx512() by
initializing the full %rax return register instead of just %al.
Technically this is unnecessary, since these functions return bool.  But
I think it's worth being extra careful with the result of the tag
comparison and also keeping the different implementations consistent.

Signed-off-by: Eric Biggers <ebiggers@...nel.org>
---

This patch is targeting libcrypto-next

 arch/x86/crypto/aes-gcm-vaes-avx2.S | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/crypto/aes-gcm-vaes-avx2.S b/arch/x86/crypto/aes-gcm-vaes-avx2.S
index d9754e683bde..93c9504a488f 100644
--- a/arch/x86/crypto/aes-gcm-vaes-avx2.S
+++ b/arch/x86/crypto/aes-gcm-vaes-avx2.S
@@ -1121,10 +1121,11 @@ SYM_FUNC_END(aes_gcm_aad_update_vaes_avx2)
 	vpxor		(%rax), GHASH_ACC, GHASH_ACC
 	vaesenclast	GHASH_ACC, %xmm0, %xmm0
 	lea		.Lselect_high_bytes_table(%rip), %rax
 	vmovdqu		(%rax, TAGLEN64), %xmm1
 	vpshufb		BSWAP_MASK, %xmm1, %xmm1 // select low bytes, not high
+	xor		%eax, %eax
 	vptest		%xmm1, %xmm0
 	sete		%al
 .endif
 	// No need for vzeroupper here, since only used xmm registers were used.
 	RET

base-commit: 5a2a5e62a5216ba05d4481cf90d915f4de0bfde9
-- 
2.51.2