xfrm_user: uncoditionally validate esn replay attribute struct

The sanity test added in ecd7918 can be bypassed, validation only occurs if XFRM_STATE_ESN flag is set, but rest of code doesn't care and just checks if the attribute itself is present. So always validate. Alternative is to reject if we have the attribute without the flag but that would change abi. Reported-by: [email protected] Cc: Mathias Krause <[email protected]> Fixes: ecd7918 ("xfrm_user: ensure user supplied esn replay window is valid") Fixes: d8647b7 ("xfrm: Add user interface for esn and big anti-replay windows") Signed-off-by: Florian Westphal <[email protected]> Signed-off-by: Steffen Klassert <[email protected]>
josf · Feb 13, 2018 · d97ca5d · d97ca5d
1 parent 2471c98
commit d97ca5d
Showing 1 changed file with 8 additions and 13 deletions.
diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
@@ -121,22 +121,17 @@ static inline int verify_replay(struct xfrm_usersa_info *p,
 	struct nlattr *rt = attrs[XFRMA_REPLAY_ESN_VAL];
 	struct xfrm_replay_state_esn *rs;
 
-	if (p->flags & XFRM_STATE_ESN) {
-		if (!rt)
-			return -EINVAL;
+	if (!rt)
+		return (p->flags & XFRM_STATE_ESN) ? -EINVAL : 0;
 
-		rs = nla_data(rt);
+	rs = nla_data(rt);
 
-		if (rs->bmp_len > XFRMA_REPLAY_ESN_MAX / sizeof(rs->bmp[0]) / 8)
-			return -EINVAL;
-
-		if (nla_len(rt) < (int)xfrm_replay_state_esn_len(rs) &&
-		    nla_len(rt) != sizeof(*rs))
-			return -EINVAL;
-	}
+	if (rs->bmp_len > XFRMA_REPLAY_ESN_MAX / sizeof(rs->bmp[0]) / 8)
+		return -EINVAL;
 
-	if (!rt)
-		return 0;
+	if (nla_len(rt) < (int)xfrm_replay_state_esn_len(rs) &&
+	    nla_len(rt) != sizeof(*rs))
+		return -EINVAL;
 
 	/* As only ESP and AH support ESN feature. */
 	if ((p->id.proto != IPPROTO_ESP) && (p->id.proto != IPPROTO_AH))