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>

1 files changed, 7 insertions, 6 deletions

diff --git a/crypto/af_alg.c b/crypto/af_alg.c
index 85cea9de324a..1e5353f62067 100644
--- 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);