Patch "sctp: fix sleep in atomic context bug in timer handlers" 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

    sctp: fix sleep in atomic context bug in timer handlers

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:
     sctp-fix-sleep-in-atomic-context-bug-in-timer-handle.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 0a89b0d48a5670c7b1ad83536469539f8b6453e1
Author: Duoming Zhou <duoming@xxxxxxxxxx>
Date:   Sat Jul 23 09:58:09 2022 +0800

    sctp: fix sleep in atomic context bug in timer handlers
    
    [ Upstream commit b89fc26f741d9f9efb51cba3e9b241cf1380ec5a ]
    
    There are sleep in atomic context bugs in timer handlers of sctp
    such as sctp_generate_t3_rtx_event(), sctp_generate_probe_event(),
    sctp_generate_t1_init_event(), sctp_generate_timeout_event(),
    sctp_generate_t3_rtx_event() and so on.
    
    The root cause is sctp_sched_prio_init_sid() with GFP_KERNEL parameter
    that may sleep could be called by different timer handlers which is in
    interrupt context.
    
    One of the call paths that could trigger bug is shown below:
    
          (interrupt context)
    sctp_generate_probe_event
      sctp_do_sm
        sctp_side_effects
          sctp_cmd_interpreter
            sctp_outq_teardown
              sctp_outq_init
                sctp_sched_set_sched
                  n->init_sid(..,GFP_KERNEL)
                    sctp_sched_prio_init_sid //may sleep
    
    This patch changes gfp_t parameter of init_sid in sctp_sched_set_sched()
    from GFP_KERNEL to GFP_ATOMIC in order to prevent sleep in atomic
    context bugs.
    
    Fixes: 5bbbbe32a431 ("sctp: introduce stream scheduler foundations")
    Signed-off-by: Duoming Zhou <duoming@xxxxxxxxxx>
    Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
    Link: https://lore.kernel.org/r/20220723015809.11553-1-duoming@xxxxxxxxxx
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/sctp/stream_sched.c b/net/sctp/stream_sched.c
index a6c04a94b08f..3a5c0d00e96c 100644
--- a/net/sctp/stream_sched.c
+++ b/net/sctp/stream_sched.c
@@ -178,7 +178,7 @@ int sctp_sched_set_sched(struct sctp_association *asoc,
 		if (!SCTP_SO(&asoc->stream, i)->ext)
 			continue;
 
-		ret = n->init_sid(&asoc->stream, i, GFP_KERNEL);
+		ret = n->init_sid(&asoc->stream, i, GFP_ATOMIC);
 		if (ret)
 			goto err;
 	}