bpf: sockmap missing NULL psock check
Add psock NULL check to handle a racing sock event that can get the sk_callback_lock before this case but after xchg happens causing the refcnt to hit zero and sock user data (psock) to be null and queued for garbage collection. Also add a comment in the code because this is a bit subtle and not obvious in my opinion. Signed-off-by: John Fastabend <john.fastabend@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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@ -591,8 +591,15 @@ static void sock_map_free(struct bpf_map *map)
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write_lock_bh(&sock->sk_callback_lock);
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psock = smap_psock_sk(sock);
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smap_list_remove(psock, &stab->sock_map[i]);
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smap_release_sock(psock, sock);
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/* This check handles a racing sock event that can get the
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* sk_callback_lock before this case but after xchg happens
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* causing the refcnt to hit zero and sock user data (psock)
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* to be null and queued for garbage collection.
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*/
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if (likely(psock)) {
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smap_list_remove(psock, &stab->sock_map[i]);
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smap_release_sock(psock, sock);
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}
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write_unlock_bh(&sock->sk_callback_lock);
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}
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rcu_read_unlock();
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