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authorBart Van Assche <bvanassche@acm.org>2019-03-25 10:01:46 -0700
committerMartin K. Petersen <martin.petersen@oracle.com>2019-03-27 21:21:38 -0400
commitc14a57264399efd39514a2329c591a4b954246d8 (patch)
tree3205f8e7c0fe838ed09fad3913b40ba6c01d417a /drivers/scsi/sd.c
parent70fc085c5015c54a7b8742a45fc9ab05d6da90da (diff)
scsi: sd: Fix a race between closing an sd device and sd I/O
The scsi_end_request() function calls scsi_cmd_to_driver() indirectly and hence needs the disk->private_data pointer. Avoid that that pointer is cleared before all affected I/O requests have finished. This patch avoids that the following crash occurs: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 Call trace: scsi_mq_uninit_cmd+0x1c/0x30 scsi_end_request+0x7c/0x1b8 scsi_io_completion+0x464/0x668 scsi_finish_command+0xbc/0x160 scsi_eh_flush_done_q+0x10c/0x170 sas_scsi_recover_host+0x84c/0xa98 [libsas] scsi_error_handler+0x140/0x5b0 kthread+0x100/0x12c ret_from_fork+0x10/0x18 Cc: Christoph Hellwig <hch@lst.de> Cc: Ming Lei <ming.lei@redhat.com> Cc: Hannes Reinecke <hare@suse.com> Cc: Johannes Thumshirn <jthumshirn@suse.de> Cc: Jason Yan <yanaijie@huawei.com> Cc: <stable@vger.kernel.org> Signed-off-by: Bart Van Assche <bvanassche@acm.org> Reported-by: Jason Yan <yanaijie@huawei.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Diffstat (limited to 'drivers/scsi/sd.c')
-rw-r--r--drivers/scsi/sd.c19
1 files changed, 13 insertions, 6 deletions
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 251db30d0882..3ffa34dc2fd5 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -1415,11 +1415,6 @@ static void sd_release(struct gendisk *disk, fmode_t mode)
scsi_set_medium_removal(sdev, SCSI_REMOVAL_ALLOW);
}
- /*
- * XXX and what if there are packets in flight and this close()
- * XXX is followed by a "rmmod sd_mod"?
- */
-
scsi_disk_put(sdkp);
}
@@ -3505,9 +3500,21 @@ static void scsi_disk_release(struct device *dev)
{
struct scsi_disk *sdkp = to_scsi_disk(dev);
struct gendisk *disk = sdkp->disk;
-
+ struct request_queue *q = disk->queue;
+
ida_free(&sd_index_ida, sdkp->index);
+ /*
+ * Wait until all requests that are in progress have completed.
+ * This is necessary to avoid that e.g. scsi_end_request() crashes
+ * due to clearing the disk->private_data pointer. Wait from inside
+ * scsi_disk_release() instead of from sd_release() to avoid that
+ * freezing and unfreezing the request queue affects user space I/O
+ * in case multiple processes open a /dev/sd... node concurrently.
+ */
+ blk_mq_freeze_queue(q);
+ blk_mq_unfreeze_queue(q);
+
disk->private_data = NULL;
put_disk(disk);
put_device(&sdkp->device->sdev_gendev);