xfrm: fix uctx len check in verify_sec_ctx_len

It's not sufficient to do 'uctx->len != (sizeof(struct xfrm_user_sec_ctx) +
uctx->ctx_len)' check only, as uctx->len may be greater than nla_len(rt),
in which case it will cause slab-out-of-bounds when accessing uctx->ctx_str
later.

This patch is to fix it by return -EINVAL when uctx->len > nla_len(rt).

Fixes: df71837d5024 ("[LSM-IPSec]: Security association restriction.")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index b88ba45..38ff02d 100644 (file)
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -110,7 +110,8 @@ static inline int verify_sec_ctx_len(struct nlattr **attrs)
                return 0;
 
        uctx = nla_data(rt);
-       if (uctx->len != (sizeof(struct xfrm_user_sec_ctx) + uctx->ctx_len))
+       if (uctx->len > nla_len(rt) ||
+           uctx->len != (sizeof(struct xfrm_user_sec_ctx) + uctx->ctx_len))
                return -EINVAL;
 
        return 0;