From: Xin Long <lucien.xin@gmail.com> stable inclusion from stable-v5.10.114 commit 61a89d0a5bcef602349e73ea016ab86b78a6a4df category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I5IY1V Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ 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> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> Acked-by: Xie XiuQi <xiexiuqi@huawei.com> --- 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 0948f14ce221..d4e5969771f0 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, -- 2.20.1