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bpf, sockmap: fix map elem deletion race with smap_stop_sock
The smap_start_sock() and smap_stop_sock() are each protected under the sock->sk_callback_lock from their call-sites except in the case of sock_map_delete_elem() where we drop the old socket from the map slot. This is racy because the same sock could be part of multiple sock maps, so we run smap_stop_sock() in parallel, and given at that point psock->strp_enabled might be true on both CPUs, we might for example wrongly restore the sk->sk_data_ready / sk->sk_write_space. Therefore, hold the sock->sk_callback_lock as well on delete. Looks like2f857d0460
("bpf: sockmap, remove STRPARSER map_flags and add multi-map support") had this right, but later one9db4ef6bf
("bpf: sockhash fix omitted bucket lock in sock_close") removed it again from delete leaving this smap_stop_sock() instance unprotected. Fixes:e9db4ef6bf
("bpf: sockhash fix omitted bucket lock in sock_close") Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: John Fastabend <john.fastabend@gmail.com> Acked-by: Song Liu <songliubraving@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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1 changed files with 4 additions and 1 deletions
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@ -1786,8 +1786,11 @@ static int sock_map_delete_elem(struct bpf_map *map, void *key)
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if (!psock)
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goto out;
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if (psock->bpf_parse)
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if (psock->bpf_parse) {
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write_lock_bh(&sock->sk_callback_lock);
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smap_stop_sock(psock, sock);
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write_unlock_bh(&sock->sk_callback_lock);
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}
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smap_list_map_remove(psock, &stab->sock_map[k]);
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smap_release_sock(psock, sock);
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out:
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