sctp: fix sleep in atomic context bug in timer handlers

BugLink: https://bugs.launchpad.net/bugs/1989218
[ 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@zju.edu.cn>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Link: https://lore.kernel.org/r/20220723015809.11553-1-duoming@zju.edu.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/net/sctp/stream_sched.c b/net/sctp/stream_sched.c
index 99e5f69fbb7424e0f72f82f140880a9c7b84b2da..a2e1d34f52c5b002cc2cefdb8c78f996856e7cb8 100644 (file)
--- a/net/sctp/stream_sched.c
+++ b/net/sctp/stream_sched.c
@@ -163,7 +163,7 @@ 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;
        }