diff options
| author | Liu Jian <liujian56@huawei.com> | 2021-10-12 13:20:19 +0800 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2021-10-26 12:25:55 -0700 |
| commit | cd9733f5d75c94a32544d6ce5be47e14194cf137 (patch) | |
| tree | 482cbaa3434e39675f0dfe9e30d8f8b8ac64184f /net/ipv4 | |
| parent | 04f8ef5643bcd8bcde25dfdebef998aea480b2ba (diff) | |
tcp_bpf: Fix one concurrency problem in the tcp_bpf_send_verdict function
With two Msgs, msgA and msgB and a user doing nonblocking sendmsg calls (or
multiple cores) on a single socket 'sk' we could get the following flow.
msgA, sk msgB, sk
----------- ---------------
tcp_bpf_sendmsg()
lock(sk)
psock = sk->psock
tcp_bpf_sendmsg()
lock(sk) ... blocking
tcp_bpf_send_verdict
if (psock->eval == NONE)
psock->eval = sk_psock_msg_verdict
..
< handle SK_REDIRECT case >
release_sock(sk) < lock dropped so grab here >
ret = tcp_bpf_sendmsg_redir
psock = sk->psock
tcp_bpf_send_verdict
lock_sock(sk) ... blocking on B
if (psock->eval == NONE) <- boom.
psock->eval will have msgA state
The problem here is we dropped the lock on msgA and grabbed it with msgB.
Now we have old state in psock and importantly psock->eval has not been
cleared. So msgB will run whatever action was done on A and the verdict
program may never see it.
Fixes: 604326b41a6fb ("bpf, sockmap: convert to generic sk_msg interface")
Signed-off-by: Liu Jian <liujian56@huawei.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20211012052019.184398-1-liujian56@huawei.com
Diffstat (limited to 'net/ipv4')
| -rw-r--r-- | net/ipv4/tcp_bpf.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c index d3e9386b493e..9d068153c316 100644 --- a/net/ipv4/tcp_bpf.c +++ b/net/ipv4/tcp_bpf.c @@ -232,6 +232,7 @@ static int tcp_bpf_send_verdict(struct sock *sk, struct sk_psock *psock, bool cork = false, enospc = sk_msg_full(msg); struct sock *sk_redir; u32 tosend, delta = 0; + u32 eval = __SK_NONE; int ret; more_data: @@ -275,13 +276,24 @@ more_data: case __SK_REDIRECT: sk_redir = psock->sk_redir; sk_msg_apply_bytes(psock, tosend); + if (!psock->apply_bytes) { + /* Clean up before releasing the sock lock. */ + eval = psock->eval; + psock->eval = __SK_NONE; + psock->sk_redir = NULL; + } if (psock->cork) { cork = true; psock->cork = NULL; } sk_msg_return(sk, msg, tosend); release_sock(sk); + ret = tcp_bpf_sendmsg_redir(sk_redir, msg, tosend, flags); + + if (eval == __SK_REDIRECT) + sock_put(sk_redir); + lock_sock(sk); if (unlikely(ret < 0)) { int free = sk_msg_free_nocharge(sk, msg); |