net: xfrm: fix memory leak in xfrm_user_rcv_msg

Syzbot reported memory leak in xfrm_user_rcv_msg(). The
problem was is non-freed skb's frag_list.

In skb_release_all() skb_release_data() will be called only
in case of skb->head != NULL, but netlink_skb_destructor()
sets head to NULL. So, allocated frag_list skb should be
freed manualy, since consume_skb() won't take care of it

Fixes: 5106f4a8acff ("xfrm/compat: Add 32=>64-bit messages translator")
Reported-and-tested-by: syzbot+fb347cf82c73a90efcca@syzkaller.appspotmail.com
Signed-off-by: Pavel Skripkin <paskripkin@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 b47d613409b70ad2c290c8542474ea2ea7e8b678..7aff641c717d7cdc45711c610f0e4fbc1fc718b6 100644 (file)
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -2811,6 +2811,16 @@ static int xfrm_user_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
 
        err = link->doit(skb, nlh, attrs);
 
+       /* We need to free skb allocated in xfrm_alloc_compat() before
+        * returning from this function, because consume_skb() won't take
+        * care of frag_list since netlink destructor sets
+        * sbk->head to NULL. (see netlink_skb_destructor())
+        */
+       if (skb_has_frag_list(skb)) {
+               kfree_skb(skb_shinfo(skb)->frag_list);
+               skb_shinfo(skb)->frag_list = NULL;
+       }
+
 err:
        kvfree(nlh64);
        return err;