linux-kernel - [PATCH 4.14 006/178] crypto: af_alg - fix NULL pointer dereference in

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Date:   Mon, 18 Dec 2017 16:47:22 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, syzbot <syzkaller@...glegroups.com>,
        Eric Biggers <ebiggers@...gle.com>,
        Stephan Mueller <smueller@...onox.de>,
        Herbert Xu <herbert@...dor.apana.org.au>
Subject: [PATCH 4.14 006/178] crypto: af_alg - fix NULL pointer dereference in

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

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

From: Eric Biggers <ebiggers@...gle.com>

commit 887207ed9e5812ed9239b6d07185a2d35dda91db upstream.

 af_alg_free_areq_sgls()

If allocating the ->tsgl member of 'struct af_alg_async_req' failed,
during cleanup we dereferenced the NULL ->tsgl pointer in
af_alg_free_areq_sgls(), because ->tsgl_entries was nonzero.

Fix it by only freeing the ->tsgl list if it is non-NULL.

This affected both algif_skcipher and algif_aead.

Fixes: e870456d8e7c ("crypto: algif_skcipher - overhaul memory management")
Fixes: d887c52d6ae4 ("crypto: algif_aead - overhaul memory management")
Reported-by: syzbot <syzkaller@...glegroups.com>
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
Reviewed-by: Stephan Mueller <smueller@...onox.de>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 crypto/af_alg.c |   13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

--- a/crypto/af_alg.c
+++ b/crypto/af_alg.c
@@ -699,14 +699,15 @@ void af_alg_free_areq_sgls(struct af_alg
 	}
 
 	tsgl = areq->tsgl;
-	for_each_sg(tsgl, sg, areq->tsgl_entries, i) {
-		if (!sg_page(sg))
-			continue;
-		put_page(sg_page(sg));
-	}
+	if (tsgl) {
+		for_each_sg(tsgl, sg, areq->tsgl_entries, i) {
+			if (!sg_page(sg))
+				continue;
+			put_page(sg_page(sg));
+		}
 
-	if (areq->tsgl && areq->tsgl_entries)
 		sock_kfree_s(sk, tsgl, areq->tsgl_entries * sizeof(*tsgl));
+	}
 }
 EXPORT_SYMBOL_GPL(af_alg_free_areq_sgls);