Commit 821362a2 authored Feb 27, 2023 by Eric Dumazet Committed by Greg Kroah-Hartman Mar 11, 2023

tcp: tcp_check_req() can be called from process context

[ Upstream commit 580f98cc33a260bb8c6a39ae2921b29586b84fdf ]

This is a follow up of commit 0a375c822497 ("tcp: tcp_rtx_synack()
can be called from process context").

Frederick Lawler reported another "__this_cpu_add() in preemptible"
warning caused by the same reason.

In my former patch I took care of tcp_rtx_synack()
but forgot that tcp_check_req() also contained some SNMP updates.

Note that some parts of tcp_check_req() always run in BH context,
I added a comment to clarify this.

Fixes: 8336886f ("tcp: TCP Fast Open Server - support TFO listeners")
Link: https://lore.kernel.org/netdev/8cd33923-a21d-397c-e46b-2a068c287b03@cloudflare.com/T/


Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Frederick Lawler <fred@cloudflare.com>
Tested-by: Frederick Lawler <fred@cloudflare.com>
Link: https://lore.kernel.org/r/20230227083336.4153089-1-edumazet@google.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent 77606e38

net/ipv4/tcp_minisocks.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -563,6 +563,9 @@ EXPORT_SYMBOL(tcp_create_openreq_child);
		* validation and inside tcp_v4_reqsk_send_ack(). Can we do better?
		*
		* We don't need to initialize tmp_opt.sack_ok as we don't use the results
		*
		* Note: If @fastopen is true, this can be called from process context.
		* Otherwise, this is from BH context.
		*/

		struct sock tcp_check_req(struct sock sk, struct sk_buff *skb,
		@@ -715,7 +718,7 @@ struct sock tcp_check_req(struct sock sk, struct sk_buff *skb,
		&tcp_rsk(req)->last_oow_ack_time))
		req->rsk_ops->send_ack(sk, skb, req);
		if (paws_reject)
		__NET_INC_STATS(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
		NET_INC_STATS(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
		return NULL;
		}

		@@ -734,7 +737,7 @@ struct sock tcp_check_req(struct sock sk, struct sk_buff *skb,
		* "fourth, check the SYN bit"
		*/
		if (flg & (TCP_FLAG_RST\|TCP_FLAG_SYN)) {
		__TCP_INC_STATS(sock_net(sk), TCP_MIB_ATTEMPTFAILS);
		TCP_INC_STATS(sock_net(sk), TCP_MIB_ATTEMPTFAILS);
		goto embryonic_reset;
		}