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sock_map: Fix a potential use-after-free in sock_map_close()

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The last refcnt of the psock can be gone right after
sock_map_remove_links(), so sk_psock_stop() could trigger a UAF.
The reason why I placed sk_psock_stop() there is to avoid RCU read
critical section, and more importantly, some callee of
sock_map_remove_links() is supposed to be called with RCU read lock,
we can not simply get rid of RCU read lock here. Therefore, the only
choice we have is to grab an additional refcnt with sk_psock_get()
and put it back after sk_psock_stop().

Fixes: 799aa7f98d ("skmsg: Avoid lock_sock() in sk_psock_backlog()")
Reported-by: syzbot+7b6548ae483d6f4c64ae@syzkaller.appspotmail.com
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/bpf/20210408030556.45134-1-xiyou.wangcong@gmail.com
This commit is contained in:
Cong Wang 2021-04-07 20:05:56 -07:00 committed by Daniel Borkmann
parent 51e0158a54
commit aadb2bb83f
1 changed files with 2 additions and 1 deletions
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3
net/core/sock_map.c
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@ -1521,7 +1521,7 @@ void sock_map_close(struct sock *sk, long timeout)
lock_sock(sk);
rcu_read_lock();
psock = sk_psock(sk);
psock = sk_psock_get(sk);
if (unlikely(!psock)) {
rcu_read_unlock();
release_sock(sk);
@ -1532,6 +1532,7 @@ void sock_map_close(struct sock *sk, long timeout)
sock_map_remove_links(sk, psock);
rcu_read_unlock();
sk_psock_stop(psock, true);
sk_psock_put(sk, psock);
release_sock(sk);
saved_close(sk, timeout);
}