crypto: af_alg - fix NULL pointer dereference in

 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@googlegroups.com>
Cc: <stable@vger.kernel.org> # v4.14+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/crypto/af_alg.c b/crypto/af_alg.c
index 85cea9de324a4f577bcbfb273d8f3a8917ca60e6..1e5353f6206724eccdbcf1e69de6d520dcc902c6 100644 (file)
--- a/crypto/af_alg.c
+++ b/crypto/af_alg.c
@@ -672,14 +672,15 @@ void af_alg_free_areq_sgls(struct af_alg_async_req *areq)
        }
 
        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);