[PATCH 3.18 34/35] crypto: algif_skcipher - Load TX SG list after waiting

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Herbert Xu <herbert@gondor.apana.org.au>

commit 4f0414e54e4d1893c6f08260693f8ef84c929293 upstream.

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

[connoro@google.com: backport to 3.18, where the relevant logic is
located in skcipher_recvmsg() rather than skcipher_recvmsg_sync()]

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Connor O'Brien <connoro@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 crypto/algif_skcipher.c |   14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

--- a/crypto/algif_skcipher.c
+++ b/crypto/algif_skcipher.c
@@ -448,13 +448,6 @@ static int skcipher_recvmsg(struct kiocb
 		char __user *from = iov->iov_base;
 
 		while (seglen) {
-			sgl = list_first_entry(&ctx->tsgl,
-					       struct skcipher_sg_list, list);
-			sg = sgl->sg;
-
-			while (!sg->length)
-				sg++;
-
 			used = ctx->used;
 			if (!used) {
 				err = skcipher_wait_for_data(sk, flags);
@@ -476,6 +469,13 @@ static int skcipher_recvmsg(struct kiocb
 			if (!used)
 				goto free;
 
+			sgl = list_first_entry(&ctx->tsgl,
+					       struct skcipher_sg_list, list);
+			sg = sgl->sg;
+
+			while (!sg->length)
+				sg++;
+
 			ablkcipher_request_set_crypt(&ctx->req, sg,
 						     ctx->rsgl.sg, used,
 						     ctx->iv);