xfrm_user: uncoditionally validate esn replay attribute struct

[ Upstream commit d97ca5d714a5334aecadadf696875da40f1fbf3e ]

The sanity test added in ecd7918745234 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: syzbot+0ab777c27d2bb7588f73@syzkaller.appspotmail.com
Cc: Mathias Krause <minipli@googlemail.com>
Fixes: ecd7918745234 ("xfrm_user: ensure user supplied esn replay window is valid")
Fixes: d8647b79c3b7e ("xfrm: Add user interface for esn and big anti-replay windows")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>

diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index 84541b35629a5c9538f86990199da52f5fd3df5e..65c18fc9bbd04395ecef4620da2c91ceb8f67e19 100644 (file)
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -120,22 +120,17 @@ 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) < 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) < 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))