From: Xin Long lucien.xin@gmail.com
[ Upstream commit 165e3e17fe8fe6a8aab319bc6e631a2e23b9a857 ]
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@redhat.com Signed-off-by: Xin Long lucien.xin@gmail.com Acked-by: Marcelo Ricardo Leitner marcelo.leitner@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- 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 2a94240eac36..82d96441e64d 100644 --- a/net/sctp/sm_sideeffect.c +++ b/net/sctp/sm_sideeffect.c @@ -473,6 +473,10 @@ 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,