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Subject[PATCH v2 5/5] scsi: libsas: fix a race condition when smp task timeout
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

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

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 <>
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 52222940d398..0d1f72752ca2 100644
--- a/drivers/scsi/libsas/sas_expander.c
+++ b/drivers/scsi/libsas/sas_expander.c
@@ -48,17 +48,16 @@ static void smp_task_timedout(struct timer_list *t)
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);

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