linux-kernel - [PATCH 5.4 26/34] sctp: fix sleep in atomic context bug in timer handlers

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Date:   Mon,  1 Aug 2022 13:47:06 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Duoming Zhou <duoming@....edu.cn>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 26/34] sctp: fix sleep in atomic context bug in timer handlers

From: Duoming Zhou <duoming@....edu.cn>

[ 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@....edu.cn>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Link: https://lore.kernel.org/r/20220723015809.11553-1-duoming@zju.edu.cn
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/sctp/stream_sched.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sctp/stream_sched.c b/net/sctp/stream_sched.c
index 99e5f69fbb74..a2e1d34f52c5 100644
--- 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;
 	}
-- 
2.35.1