[patch 36/43] crypto: authenc - Fix zero-length IV crash

[Greg KH]

2.6.28-stable review patch.  If anyone has any objections, please let us know.

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

From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>

commit 29b37f42127f7da511560a40ea74f5047da40c13 upstream.

As it is if an algorithm with a zero-length IV is used (e.g.,
NULL encryption) with authenc, authenc may generate an SG entry
of length zero, which will trigger a BUG check in the hash layer.

This patch fixes it by skipping the IV SG generation if the IV
size is zero.

Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 crypto/authenc.c |   24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

--- a/crypto/authenc.c
+++ b/crypto/authenc.c
@@ -157,16 +157,19 @@ static int crypto_authenc_genicv(struct 
 	dstp = sg_page(dst);
 	vdst = PageHighMem(dstp) ? NULL : page_address(dstp) + dst->offset;
 
-	sg_init_table(cipher, 2);
-	sg_set_buf(cipher, iv, ivsize);
-	authenc_chain(cipher, dst, vdst == iv + ivsize);
+	if (ivsize) {
+		sg_init_table(cipher, 2);
+		sg_set_buf(cipher, iv, ivsize);
+		authenc_chain(cipher, dst, vdst == iv + ivsize);
+		dst = cipher;
+	}
 
 	cryptlen = req->cryptlen + ivsize;
-	hash = crypto_authenc_hash(req, flags, cipher, cryptlen);
+	hash = crypto_authenc_hash(req, flags, dst, cryptlen);
 	if (IS_ERR(hash))
 		return PTR_ERR(hash);
 
-	scatterwalk_map_and_copy(hash, cipher, cryptlen,
+	scatterwalk_map_and_copy(hash, dst, cryptlen,
 				 crypto_aead_authsize(authenc), 1);
 	return 0;
 }
@@ -284,11 +287,14 @@ static int crypto_authenc_iverify(struct
 	srcp = sg_page(src);
 	vsrc = PageHighMem(srcp) ? NULL : page_address(srcp) + src->offset;
 
-	sg_init_table(cipher, 2);
-	sg_set_buf(cipher, iv, ivsize);
-	authenc_chain(cipher, src, vsrc == iv + ivsize);
+	if (ivsize) {
+		sg_init_table(cipher, 2);
+		sg_set_buf(cipher, iv, ivsize);
+		authenc_chain(cipher, src, vsrc == iv + ivsize);
+		src = cipher;
+	}
 
-	return crypto_authenc_verify(req, cipher, cryptlen + ivsize);
+	return crypto_authenc_verify(req, src, cryptlen + ivsize);
 }
 
 static int crypto_authenc_decrypt(struct aead_request *req)

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