From a466856e0b7ab269cdf9461886d007e88ff575b0 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Sat, 7 Apr 2018 13:42:36 -0700
Subject: [PATCH] crypto: af_alg - fix possible uninit-value in alg_bind()
Git-commit: a466856e0b7ab269cdf9461886d007e88ff575b0
Patch-mainline: v4.17-rc1
References: bsc#1051510

syzbot reported :

Bug: KMSAN: uninit-value in alg_bind+0xe3/0xd90 crypto/af_alg.c:162

We need to check addr_len before dereferencing sa (or uaddr)

Fixes: bb30b8848c85 ("crypto: af_alg - whitelist mask and type")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Cc: Stephan Mueller <smueller@chronox.de>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 crypto/af_alg.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/crypto/af_alg.c
+++ b/crypto/af_alg.c
@@ -157,16 +157,16 @@ static int alg_bind(struct socket *sock,
 	void *private;
 	int err;
 
-	/* If caller uses non-allowed flag, return error. */
-	if ((sa->salg_feat & ~allowed) || (sa->salg_mask & ~allowed))
-		return -EINVAL;
-
 	if (sock->state == SS_CONNECTED)
 		return -EINVAL;
 
 	if (addr_len < sizeof(*sa))
 		return -EINVAL;
 
+	/* If caller uses non-allowed flag, return error. */
+	if ((sa->salg_feat & ~allowed) || (sa->salg_mask & ~allowed))
+		return -EINVAL;
+
 	sa->salg_type[sizeof(sa->salg_type) - 1] = 0;
 	sa->salg_name[sizeof(sa->salg_name) + addr_len - sizeof(*sa) - 1] = 0;