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scsi: bnx2fc: Plug CPU hotplug race

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bnx2fc_process_new_cqes() has protection against CPU hotplug, which relies
on the per cpu thread pointer. This protection is racy because it happens
only partially with the per cpu fp_work_lock held.

If the CPU is unplugged after the lock is dropped, the wakeup code can
dereference a NULL pointer or access freed and potentially reused memory.

Restructure the code so the thread check and wakeup happens with the
fp_work_lock held.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Chad Dupuis <chad.dupuis@cavium.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Thomas Gleixner 2017-07-24 12:52:56 +02:00 committed by Martin K. Petersen
parent 2c67521821
commit 8addebc14a
1 changed files with 23 additions and 22 deletions
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45
drivers/scsi/bnx2fc/bnx2fc_hwi.c
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@ -1008,6 +1008,28 @@ static struct bnx2fc_work *bnx2fc_alloc_work(struct bnx2fc_rport *tgt, u16 wqe)
return work;
}
/* Pending work request completion */
static void bnx2fc_pending_work(struct bnx2fc_rport *tgt, unsigned int wqe)
{
unsigned int cpu = wqe % num_possible_cpus();
struct bnx2fc_percpu_s *fps;
struct bnx2fc_work *work;
fps = &per_cpu(bnx2fc_percpu, cpu);
spin_lock_bh(&fps->fp_work_lock);
if (fps->iothread) {
work = bnx2fc_alloc_work(tgt, wqe);
if (work) {
list_add_tail(&work->list, &fps->work_list);
wake_up_process(fps->iothread);
spin_unlock_bh(&fps->fp_work_lock);
return;
}
}
spin_unlock_bh(&fps->fp_work_lock);
bnx2fc_process_cq_compl(tgt, wqe);
}
int bnx2fc_process_new_cqes(struct bnx2fc_rport *tgt)
{
struct fcoe_cqe *cq;
@ -1042,28 +1064,7 @@ int bnx2fc_process_new_cqes(struct bnx2fc_rport *tgt)
/* Unsolicited event notification */
bnx2fc_process_unsol_compl(tgt, wqe);
} else {
/* Pending work request completion */
struct bnx2fc_work *work = NULL;
struct bnx2fc_percpu_s *fps = NULL;
unsigned int cpu = wqe % num_possible_cpus();
fps = &per_cpu(bnx2fc_percpu, cpu);
spin_lock_bh(&fps->fp_work_lock);
if (unlikely(!fps->iothread))
goto unlock;
work = bnx2fc_alloc_work(tgt, wqe);
if (work)
list_add_tail(&work->list,
&fps->work_list);
unlock:
spin_unlock_bh(&fps->fp_work_lock);
/* Pending work request completion */
if (fps->iothread && work)
wake_up_process(fps->iothread);
else
bnx2fc_process_cq_compl(tgt, wqe);
bnx2fc_pending_work(tgt, wqe);
num_free_sqes++;
}
cqe++;