A null pointer reference issue can be triggered when the response of a
stream reconf request arrives after the timer is triggered, such as:
send Incoming SSN Reset Request --->
CPU0:
reconf timer is triggered,
go to the handler code before hold sk lock
<--- reply with Outgoing SSN Reset Request
CPU1:
process Outgoing SSN Reset Request,
and set asoc->strreset_chunk to NULL
CPU0:
continue the handler code, hold sk lock,
and try to hold asoc->strreset_chunk, crash!
In Ying Xu's testing, the call trace is:
[ ] BUG: kernel NULL pointer dereference, address: 0000000000000010
[ ] RIP: 0010:sctp_chunk_hold+0xe/0x40 [sctp]
[ ] Call Trace:
[ ] <IRQ>
[ ] sctp_sf_send_reconf+0x2c/0x100 [sctp]
[ ] sctp_do_sm+0xa4/0x220 [sctp]
[ ] sctp_generate_reconf_event+0xbd/0xe0 [sctp]
[ ] call_timer_fn+0x26/0x130
This patch is to fix it by returning from the timer handler if asoc
strreset_chunk is already set to NULL.
Fixes: 7b9438de0cd4 ("sctp: add stream reconf timer")
Reported-by: Ying Xu <yinxu@xxxxxxxxxx>
Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
---
net/sctp/sm_sideeffect.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/net/sctp/sm_sideeffect.c b/net/sctp/sm_sideeffect.c
index b3815b568e8e..463c4a58d2c3 100644
--- a/net/sctp/sm_sideeffect.c
+++ b/net/sctp/sm_sideeffect.c
@@ -458,6 +458,10 @@ void sctp_generate_reconf_event(struct timer_list *t)
goto out_unlock;
}
+ /* This happens when the response arrives after the timer is triggered. */
+ if (!asoc->strreset_chunk)
+ goto out_unlock;
+
error = sctp_do_sm(net, SCTP_EVENT_T_TIMEOUT,
SCTP_ST_TIMEOUT(SCTP_EVENT_TIMEOUT_RECONF),
asoc->state, asoc->ep, asoc,
--
2.31.1
