Re: crypto: slab-out-of-bounds in skcipher_recvmsg

[Herbert Xu]

On Fri, Jan 15, 2016 at 07:22:04PM +0100, Dmitry Vyukov wrote:
> Hello,
> 
> The following program causes slab-out-of-bounds in skcipher_recvmsg:

Thanks for the report.  This patch should fix it.

---8<---
Subject: crypto: algif_skcipher - Load TX SG list after waiting

We need to load the TX SG list in sendmsg(2) after waiting for
incoming data, not before.

Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>

diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c
index dfff8b0..df86fb4 100644
--- a/crypto/algif_skcipher.c
+++ b/crypto/algif_skcipher.c
@@ -647,13 +647,6 @@ static int skcipher_recvmsg_sync(struct socket *sock, struct msghdr *msg,
 
 	lock_sock(sk);
 	while (msg_data_left(msg)) {
-		sgl = list_first_entry(&ctx->tsgl,
-				       struct skcipher_sg_list, list);
-		sg = sgl->sg;
-
-		while (!sg->length)
-			sg++;
-
 		if (!ctx->used) {
 			err = skcipher_wait_for_data(sk, flags);
 			if (err)
@@ -674,6 +667,13 @@ static int skcipher_recvmsg_sync(struct socket *sock, struct msghdr *msg,
 		if (!used)
 			goto free;
 
+		sgl = list_first_entry(&ctx->tsgl,
+				       struct skcipher_sg_list, list);
+		sg = sgl->sg;
+
+		while (!sg->length)
+			sg++;
+
 		skcipher_request_set_crypt(&ctx->req, sg, ctx->rsgl.sg, used,
 					   ctx->iv);
 
-- 
Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/
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