From 41b5d3eee4af6a4ea488a1735ed82e4e593eec0d Mon Sep 17 00:00:00 2001 From: Jason Yan Date: Tue, 25 Sep 2018 10:56:54 +0800 Subject: [PATCH] scsi: libsas: fix a race condition when smp task timeout commit b90cd6f2b905905fb42671009dc0e27c310a16ae upstream. When the lldd is processing the complete sas task in interrupt and set the task stat as SAS_TASK_STATE_DONE, the smp timeout timer is able to be triggered at the same time. And smp_task_timedout() will complete the task wheter the SAS_TASK_STATE_DONE is set or not. Then the sas task may freed before lldd end the interrupt process. Thus a use-after-free will happen. Fix this by calling the complete() only when SAS_TASK_STATE_DONE is not set. And remove the check of the return value of the del_timer(). Once the LLDD sets DONE, it must call task->done(), which will call smp_task_done()->complete() and the task will be completed and freed correctly. CVE: CVE-2018-20836 Upstream-Status: Backport [https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-4.9.y&id=41b5d3eee4af6a4ea488a1735ed82e4e593eec0d] Reported-by: chenxiang Signed-off-by: Jason Yan CC: John Garry CC: Johannes Thumshirn CC: Ewan Milne CC: Christoph Hellwig CC: Tomas Henzl CC: Dan Williams CC: Hannes Reinecke Reviewed-by: Hannes Reinecke Reviewed-by: John Garry Reviewed-by: Johannes Thumshirn Signed-off-by: Martin K. Petersen Cc: Guenter Roeck Signed-off-by: Andreas Wellving --- drivers/scsi/libsas/sas_expander.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c index 7be581f7c35d..1a6f65db615e 100644 --- a/drivers/scsi/libsas/sas_expander.c +++ b/drivers/scsi/libsas/sas_expander.c @@ -47,17 +47,16 @@ static void smp_task_timedout(unsigned long _task) unsigned long flags; spin_lock_irqsave(&task->task_state_lock, flags); - if (!(task->task_state_flags & SAS_TASK_STATE_DONE)) + if (!(task->task_state_flags & SAS_TASK_STATE_DONE)) { task->task_state_flags |= SAS_TASK_STATE_ABORTED; + complete(&task->slow_task->completion); + } spin_unlock_irqrestore(&task->task_state_lock, flags); - - complete(&task->slow_task->completion); } static void smp_task_done(struct sas_task *task) { - if (!del_timer(&task->slow_task->timer)) - return; + del_timer(&task->slow_task->timer); complete(&task->slow_task->completion); } -- 2.20.1