Patch "tcp: tcp_check_req() can be called from process context" has been added to the 4.19-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    tcp: tcp_check_req() can be called from process context

to the 4.19-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     tcp-tcp_check_req-can-be-called-from-process-context.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 120ef4bc447462f9abdb909f5e36880edf5394cf
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date:   Mon Feb 27 08:33:36 2023 +0000

    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: 8336886f786f ("tcp: TCP Fast Open Server - support TFO listeners")
    Link: https://lore.kernel.org/netdev/8cd33923-a21d-397c-e46b-2a068c287b03@xxxxxxxxxxxxxx/T/
    Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
    Reported-by: Frederick Lawler <fred@xxxxxxxxxxxxxx>
    Tested-by: Frederick Lawler <fred@xxxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230227083336.4153089-1-edumazet@xxxxxxxxxx
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 0fc238d79b03a..bae0199a943bd 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -582,6 +582,9 @@ 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,
@@ -734,7 +737,7 @@ 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;
 	}
 
@@ -753,7 +756,7 @@ 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;
 	}