This is a note to let you know that I've just added the patch titled
scsi: qedi: Fix potential deadlock on &qedi_percpu->p_work_lock
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
scsi-qedi-fix-potential-deadlock-on-qedi_percpu-p_wo.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit c7e70aeb3dff8011544e8775d365879862ae8ded
Author: Chengfeng Ye <dg573847474@xxxxxxxxx>
Date: Wed Jul 26 12:56:55 2023 +0000
scsi: qedi: Fix potential deadlock on &qedi_percpu->p_work_lock
[ Upstream commit dd64f80587190265ca8a0f4be6c64c2fda6d3ac2 ]
As &qedi_percpu->p_work_lock is acquired by hard IRQ qedi_msix_handler(),
other acquisitions of the same lock under process context should disable
IRQ, otherwise deadlock could happen if the IRQ preempts the execution
while the lock is held in process context on the same CPU.
qedi_cpu_offline() is one such function which acquires the lock in process
context.
[Deadlock Scenario]
qedi_cpu_offline()
->spin_lock(&p->p_work_lock)
<irq>
->qedi_msix_handler()
->edi_process_completions()
->spin_lock_irqsave(&p->p_work_lock, flags); (deadlock here)
This flaw was found by an experimental static analysis tool I am developing
for IRQ-related deadlocks.
The tentative patch fix the potential deadlock by spin_lock_irqsave()
under process context.
Signed-off-by: Chengfeng Ye <dg573847474@xxxxxxxxx>
Link: https://lore.kernel.org/r/20230726125655.4197-1-dg573847474@xxxxxxxxx
Acked-by: Manish Rangankar <mrangankar@xxxxxxxxxxx>
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/scsi/qedi/qedi_main.c b/drivers/scsi/qedi/qedi_main.c
index ab66e1f0fdfa3..7a179cfc01ed2 100644
--- a/drivers/scsi/qedi/qedi_main.c
+++ b/drivers/scsi/qedi/qedi_main.c
@@ -1864,8 +1864,9 @@ static int qedi_cpu_offline(unsigned int cpu)
struct qedi_percpu_s *p = this_cpu_ptr(&qedi_percpu);
struct qedi_work *work, *tmp;
struct task_struct *thread;
+ unsigned long flags;
- spin_lock_bh(&p->p_work_lock);
+ spin_lock_irqsave(&p->p_work_lock, flags);
thread = p->iothread;
p->iothread = NULL;
@@ -1876,7 +1877,7 @@ static int qedi_cpu_offline(unsigned int cpu)
kfree(work);
}
- spin_unlock_bh(&p->p_work_lock);
+ spin_unlock_irqrestore(&p->p_work_lock, flags);
if (thread)
kthread_stop(thread);
return 0;
