From: Ming Lei <ming....@redhat.com> [ Upstream commit 831e3405c2a344018a18fcc2665acc5a38c3a707 ]
The current scanning mechanism is supposed to fall back to a synchronous host scan if an asynchronous scan is in progress. However, this rule isn't strictly respected, scsi_prep_async_scan() doesn't hold scan_mutex when checking shost->async_scan. When scsi_scan_host() is called concurrently, two async scans on same host can be started and a hang in do_scan_async() is observed. Fixes this issue by checking & setting shost->async_scan atomically with shost->scan_mutex. Link: https://lore.kernel.org/r/20201010032539.426615-1-ming....@redhat.com Cc: Christoph Hellwig <h...@lst.de> Cc: Ewan D. Milne <emi...@redhat.com> Cc: Hannes Reinecke <h...@suse.de> Cc: Bart Van Assche <bvanass...@acm.org> Reviewed-by: Lee Duncan <ldun...@suse.com> Reviewed-by: Bart Van Assche <bvanass...@acm.org> Signed-off-by: Ming Lei <ming....@redhat.com> Signed-off-by: Martin K. Petersen <martin.peter...@oracle.com> Signed-off-by: Sasha Levin <sas...@kernel.org> --- drivers/scsi/scsi_scan.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c index f2437a7570ce8..9af50e6f94c4c 100644 --- a/drivers/scsi/scsi_scan.c +++ b/drivers/scsi/scsi_scan.c @@ -1714,15 +1714,16 @@ static void scsi_sysfs_add_devices(struct Scsi_Host *shost) */ static struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost) { - struct async_scan_data *data; + struct async_scan_data *data = NULL; unsigned long flags; if (strncmp(scsi_scan_type, "sync", 4) == 0) return NULL; + mutex_lock(&shost->scan_mutex); if (shost->async_scan) { shost_printk(KERN_DEBUG, shost, "%s called twice\n", __func__); - return NULL; + goto err; } data = kmalloc(sizeof(*data), GFP_KERNEL); @@ -1733,7 +1734,6 @@ static struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost) goto err; init_completion(&data->prev_finished); - mutex_lock(&shost->scan_mutex); spin_lock_irqsave(shost->host_lock, flags); shost->async_scan = 1; spin_unlock_irqrestore(shost->host_lock, flags); @@ -1748,6 +1748,7 @@ static struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost) return data; err: + mutex_unlock(&shost->scan_mutex); kfree(data); return NULL; } -- 2.27.0
