From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, John Fastabend , Daniel Borkmann , Sasha Levin Subject: [PATCH 4.14 090/115] bpf: sockmap missing NULL psock check Date: Fri, 2 Mar 2018 09:51:33 +0100 Message-Id: <20180302084507.494931061@linuxfoundation.org> In-Reply-To: <20180302084503.856536800@linuxfoundation.org> References: <20180302084503.856536800@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: John Fastabend [ Upstream commit 5731a879d03bdaa00265f8ebc32dfd0e65d25276 ] 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 Signed-off-by: Daniel Borkmann Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- kernel/bpf/sockmap.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) --- a/kernel/bpf/sockmap.c +++ b/kernel/bpf/sockmap.c @@ -588,8 +588,15 @@ static void sock_map_free(struct bpf_map write_lock_bh(&sock->sk_callback_lock); psock = smap_psock_sk(sock); - smap_list_remove(psock, &stab->sock_map[i]); - smap_release_sock(psock, sock); + /* This check handles 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. + */ + if (likely(psock)) { + smap_list_remove(psock, &stab->sock_map[i]); + smap_release_sock(psock, sock); + } write_unlock_bh(&sock->sk_callback_lock); } rcu_read_unlock();