On Thu, 2016-03-24 at 10:56 +0100, Johannes Thumshirn wrote:
> The target state machine only knows 'STARGET_DEL', which is set once
> scsi_target_destroy() is called.
> However, by that time the structure is still part of the __stargets
> list of the SCSI host, so any concurrent invocation will see this as
> a valid target, causing an access to freed memory.
>
> This patch adds an intermediate state 'STARGET_REMOVE', which is set
> as soon as the target is scheduled to be removed.
> With this any concurrent invocation will be able to skip these
> targets and avoid the above scenario.
>
> Signed-off-by: Johannes Thumshirn <jthumshirn@xxxxxxx>
> Fixes: 90a88d6ef 'scsi: fix soft lockup in scsi_remove_target() on module removal'
> Cc: stable@xxxxxxxxxxxxxxx
> Reviewed-by: Hannes Reinecke <hare@xxxxxxxx>
> ---
> drivers/scsi/scsi_scan.c | 1 +
> drivers/scsi/scsi_sysfs.c | 2 ++
> include/scsi/scsi_device.h | 1 +
> 3 files changed, 4 insertions(+)
>
> diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
> index 6a82066..37459dfa 100644
> --- a/drivers/scsi/scsi_scan.c
> +++ b/drivers/scsi/scsi_scan.c
> @@ -315,6 +315,7 @@ static void scsi_target_destroy(struct scsi_target *starget)
> struct Scsi_Host *shost = dev_to_shost(dev->parent);
> unsigned long flags;
>
> + BUG_ON(starget->state != STARGET_REMOVE);
> starget->state = STARGET_DEL;
> transport_destroy_device(dev);
> spin_lock_irqsave(shost->host_lock, flags);
> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
> index 00bc721..0df82e8 100644
> --- a/drivers/scsi/scsi_sysfs.c
> +++ b/drivers/scsi/scsi_sysfs.c
> @@ -1279,11 +1279,13 @@ restart:
> spin_lock_irqsave(shost->host_lock, flags);
> list_for_each_entry(starget, &shost->__targets, siblings) {
> if (starget->state == STARGET_DEL ||
> + starget->state == STARGET_REMOVE ||
> starget == last_target)
> continue;
> if (starget->dev.parent == dev || &starget->dev == dev) {
> kref_get(&starget->reap_ref);
> last_target = starget;
> + starget->state = STARGET_REMOVE;
> spin_unlock_irqrestore(shost->host_lock, flags);
> __scsi_remove_target(starget);
> scsi_target_reap(starget);
> diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
> index f63a167..2bffaa6 100644
> --- a/include/scsi/scsi_device.h
> +++ b/include/scsi/scsi_device.h
> @@ -240,6 +240,7 @@ scmd_printk(const char *, const struct scsi_cmnd *, const char *, ...);
> enum scsi_target_state {
> STARGET_CREATED = 1,
> STARGET_RUNNING,
> + STARGET_REMOVE,
> STARGET_DEL,
> };
>
This looks fine. Do we still need 90a88d6ef (scsi: fix soft lockup in
scsi_remove_target() on module removal) or can that be reverted now,
since the STARGET_REMOVE state will allow the iteration to continue?
Reviewed-by: Ewan D. Milne <emilne@xxxxxxxxxx>
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