linux-kernel - [PATCH] crypto: x86/aes-ni - check walk.nbytes instead of err

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Message-Id: <20210911110759.40911-1-chouhan.shreyansh630@gmail.com>
Date:   Sat, 11 Sep 2021 16:37:59 +0530
From:   Shreyansh Chouhan <chouhan.shreyansh630@...il.com>
To:     herbert@...dor.apana.org.au, davem@...emloft.net,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, x86@...nel.org,
        hpa@...or.com
Cc:     Shreyansh Chouhan <chouhan.shreyansh630@...il.com>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: [PATCH] crypto: x86/aes-ni - check walk.nbytes instead of err

In the code for xts_crypt(), we check for the err value returned by
skcipher_walk_virt() and return from the function if it is non zero.
However, skcipher_walk_virt() can set walk.nbytes to 0, which would cause
us to call kernel_fpu_begin(), and then skip the kernel_fpu_end() call.

This patch checks for the walk.nbytes value instead, and returns if
walk.nbytes is 0. This prevents us from calling kernel_fpu_begin() in
the first place and also covers the case of having a non zero err value
returned from skcipher_walk_virt().

Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Shreyansh Chouhan <chouhan.shreyansh630@...il.com>
---
 arch/x86/crypto/aesni-intel_glue.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/crypto/aesni-intel_glue.c b/arch/x86/crypto/aesni-intel_glue.c
index 0fc961bef299..e09f4672dd38 100644
--- a/arch/x86/crypto/aesni-intel_glue.c
+++ b/arch/x86/crypto/aesni-intel_glue.c
@@ -866,7 +866,7 @@ static int xts_crypt(struct skcipher_request *req, bool encrypt)
 		req = &subreq;
 
 		err = skcipher_walk_virt(&walk, req, false);
-		if (err)
+		if (!walk.nbytes)
 			return err;
 	} else {
 		tail = 0;
-- 
2.31.1