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| author | Eric Dumazet <edumazet@google.com> | 2024-05-28 12:52:51 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-08-03 08:59:35 +0200 |
| commit | c366435a152b8e4f53f7fcf4752d81df877a39e0 (patch) | |
| tree | eaa2e59025634c79611c89049d4e8b0e1132f095 /net | |
| parent | ea734f7724ebbb7a020aa69f134dd4f6be606183 (diff) | |
| download | linux-stable-c366435a152b8e4f53f7fcf4752d81df877a39e0.tar.gz linux-stable-c366435a152b8e4f53f7fcf4752d81df877a39e0.tar.bz2 linux-stable-c366435a152b8e4f53f7fcf4752d81df877a39e0.zip | |
tcp: fix race in tcp_write_err()
[ 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: 1da177e4c3f4 ("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>
Diffstat (limited to 'net')
| -rw-r--r-- | net/ipv4/tcp_timer.c | 6 |
1 files changed, 1 insertions, 5 deletions
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c index 892c86657fbc..4d40615dc8fc 100644 --- a/net/ipv4/tcp_timer.c +++ b/net/ipv4/tcp_timer.c @@ -74,11 +74,7 @@ u32 tcp_clamp_probe0_to_user_timeout(const struct sock *sk, u32 when) static void tcp_write_err(struct sock *sk) { - WRITE_ONCE(sk->sk_err, READ_ONCE(sk->sk_err_soft) ? : ETIMEDOUT); - sk_error_report(sk); - - tcp_write_queue_purge(sk); - tcp_done(sk); + tcp_done_with_error(sk, READ_ONCE(sk->sk_err_soft) ? : ETIMEDOUT); __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONTIMEOUT); } |