4.18-stable review patch. If anyone has any objections, please let me know.
------------------ From: Daniel Borkmann <[email protected]> [ Upstream commit 166ab6f0a0702fdd4d865ad5090bf3094ed83428 ] 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 like 2f857d04601a ("bpf: sockmap, remove STRPARSER map_flags and add multi-map support") had this right, but later on e9db4ef6bf4c ("bpf: sockhash fix omitted bucket lock in sock_close") removed it again from delete leaving this smap_stop_sock() instance unprotected. Fixes: e9db4ef6bf4c ("bpf: sockhash fix omitted bucket lock in sock_close") Signed-off-by: Daniel Borkmann <[email protected]> Acked-by: John Fastabend <[email protected]> Acked-by: Song Liu <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Signed-off-by: Sasha Levin <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- kernel/bpf/sockmap.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/kernel/bpf/sockmap.c +++ b/kernel/bpf/sockmap.c @@ -1784,8 +1784,11 @@ static int sock_map_delete_elem(struct b if (!psock) goto out; - if (psock->bpf_parse) + if (psock->bpf_parse) { + write_lock_bh(&sock->sk_callback_lock); smap_stop_sock(psock, sock); + write_unlock_bh(&sock->sk_callback_lock); + } smap_list_map_remove(psock, &stab->sock_map[k]); smap_release_sock(psock, sock); out:
