commit 0cabf2af6f5ac3c88cb106c4e06087a5a39b8e1e
author Herbert Xu <herbert@gondor.apana.org.au> Sat Oct 07 11:29:48 2017 +0800
committer Herbert Xu <herbert@gondor.apana.org.au> Sat Oct 07 12:04:32 2017 +0800
tree 6d612f29ee44e877b4fb546898f729f135ac9900
parent 9039f3ef446e9ffa200200c934f049add9e58426

crypto: skcipher - Fix crash on zero-length input

The skcipher walk interface doesn't handle zero-length input
properly as the old blkcipher walk interface did.  This is due
to the fact that the length check is done too late.

This patch moves the length check forward so that it does the
right thing.

Fixes: b286d8b1a690 ("crypto: skcipher - Add skcipher walk...")
Cc: <stable@vger.kernel.org>
Reported-by: Stephan Müller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/skcipher.c

diff --git a/crypto/skcipher.c b/crypto/skcipher.c
index 4faa0fd..d5692e3 100644
--- a/crypto/skcipher.c
+++ b/crypto/skcipher.c
@@ -426,14 +426,9 @@
 
 static int skcipher_walk_first(struct skcipher_walk *walk)
 {
-	walk->nbytes = 0;
-
 	if (WARN_ON_ONCE(in_irq()))
 		return -EDEADLK;
 
-	if (unlikely(!walk->total))
-		return 0;
-
 	walk->buffer = NULL;
 	if (unlikely(((unsigned long)walk->iv & walk->alignmask))) {
 		int err = skcipher_copy_iv(walk);
@@ -452,10 +447,15 @@
 {
 	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 
+	walk->total = req->cryptlen;
+	walk->nbytes = 0;
+
+	if (unlikely(!walk->total))
+		return 0;
+
 	scatterwalk_start(&walk->in, req->src);
 	scatterwalk_start(&walk->out, req->dst);
 
-	walk->total = req->cryptlen;
 	walk->iv = req->iv;
 	walk->oiv = req->iv;
 
@@ -509,6 +509,11 @@
 	struct crypto_aead *tfm = crypto_aead_reqtfm(req);
 	int err;
 
+	walk->nbytes = 0;
+
+	if (unlikely(!walk->total))
+		return 0;
+
 	walk->flags &= ~SKCIPHER_WALK_PHYS;
 
 	scatterwalk_start(&walk->in, req->src);