bianbu-repo-mirror/bianbu-linux-6.6
1
0
Fork 0
mirror of https://gitee.com/bianbu-linux/linux-6.6 synced 2025-04-24 14:07:52 -04:00
Code Issues Projects Releases Packages Wiki Activity Actions

tcp: fix race in tcp_write_err()

Browse source 
[ Upstream commit 853c3bd7b7917670224c9fe5245bd045cac411dd ]

I noticed flakes in a packetdrill test, expecting an epoll_wait()
to return EPOLLERR | EPOLLHUP on a failed connect() attempt,
after multiple SYN retransmits. It sometimes return EPOLLERR only.

The issue is that tcp_write_err():
 1) writes an error in sk->sk_err,
 2) calls sk_error_report(),
 3) then calls tcp_done().

tcp_done() is writing SHUTDOWN_MASK into sk->sk_shutdown,
among other things.

Problem is that the awaken user thread (from 2) sk_error_report())
might call tcp_poll() before tcp_done() has written sk->sk_shutdown.

tcp_poll() only sees a non zero sk->sk_err and returns EPOLLERR.

This patch fixes the issue by making sure to call sk_error_report()
after tcp_done().

tcp_write_err() also lacks an smp_wmb().

We can reuse tcp_done_with_error() to factor out the details,
as Neal suggested.

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Link: https://lore.kernel.org/r/20240528125253.1966136-3-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Eric Dumazet 2024-05-28 12:52:51 +00:00 • committed by Greg Kroah-Hartman
parent ecc6836d63
commit bc4f9c2ccd
1 changed files with 1 additions and 5 deletions
Download patch file Download diff file Expand all files Collapse all files

6
net/ipv4/tcp_timer.c
View file

@ -69,11 +69,7 @@ u32 tcp_clamp_probe0_to_user_timeout(const struct sock *sk, u32 when)
static void tcp_write_err(struct sock *sk) static void tcp_write_err(struct sock *sk)
{ {
WRITE_ONCE(sk->sk_err, READ_ONCE(sk->sk_err_soft) ? : ETIMEDOUT); tcp_done_with_error(sk, READ_ONCE(sk->sk_err_soft) ? : ETIMEDOUT);
sk_error_report(sk);
tcp_write_queue_purge(sk);
tcp_done(sk);
__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONTIMEOUT); __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONTIMEOUT);
} }