crypto: af_alg - Initialize sg_num_bytes in error code path

commit 2546da9 upstream.

The RX SGL in processing is already registered with the RX SGL tracking
list to support proper cleanup. The cleanup code path uses the
sg_num_bytes variable which must therefore be always initialized, even
in the error code path.

Signed-off-by: Stephan Mueller <[email protected]>
Reported-by: [email protected]
#syz test: https://github.com/google/kmsan.git master
CC: <[email protected]> #4.14
Fixes: e870456 ("crypto: algif_skcipher - overhaul memory management")
Fixes: d887c52 ("crypto: algif_aead - overhaul memory management")
Signed-off-by: Herbert Xu <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: smuellerDD

crypto/af_alg.c

@@ -1183,8 +1183,10 @@ int af_alg_get_rsgl(struct sock *sk, struct msghdr *msg, int flags,
 
 		/* make one iovec available as scatterlist */
 		err = af_alg_make_sg(&rsgl->sgl, &msg->msg_iter, seglen);
-		if (err < 0)
+		if (err < 0) {
+			rsgl->sg_num_bytes = 0;
 			return err;
+		}
 
 		/* chain the new scatterlist with previous one */
 		if (areq->last_rsgl)