[PATCH v2 net-next] IPsec: do not ignore crypto err in ah input

ah input processing uses the asynchronous hash crypto API which supplies 
an error code as part of the operation completion but the error code was 
being ignored.

Treat a crypto API error indication as a verification failure.

While a crypto API reported error would almost certainly result in a 
memcmp of the digest failing anyway and thus the security risk seems 
minor, performing a memory compare on what might be uninitialized memory 
is wrong.

Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
CC: Alexander Alemayhu <redacted>
---

The change was boot tested on Arm64 but I did not exercise
the specific error code path in question.

Changes from v1:
- Fixed typo in patch description pointed out by Alexander

 net/ipv4/ah4.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/ipv4/ah4.c b/net/ipv4/ah4.c
index f2a7102..22377c8 100644
--- a/net/ipv4/ah4.c
+++ b/net/ipv4/ah4.c

@@ -270,6 +270,9 @@ static void ah_input_done(struct crypto_async_request *base, int err)
 	int ihl = ip_hdrlen(skb);
 	int ah_hlen = (ah->hdrlen + 2) << 2;
 
+	if (err)
+		goto out;
+
 	work_iph = AH_SKB_CB(skb)->tmp;
 	auth_data = ah_tmp_auth(work_iph, ihl);
 	icv = ah_tmp_icv(ahp->ahash, auth_data, ahp->icv_trunc_len);

-- 
2.1.4