4.4-stable review patch. If anyone has any objections, please let me know.
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From: Bart Van Assche bvanassche@acm.org
commit c14a57264399efd39514a2329c591a4b954246d8 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/scsi/sd.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-)
--- a/drivers/scsi/sd.c +++ b/drivers/scsi/sd.c @@ -1276,11 +1276,6 @@ static void sd_release(struct gendisk *d 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); }
@@ -3227,11 +3222,23 @@ static void scsi_disk_release(struct dev { struct scsi_disk *sdkp = to_scsi_disk(dev); struct gendisk *disk = sdkp->disk; - + struct request_queue *q = disk->queue; + spin_lock(&sd_index_lock); ida_remove(&sd_index_ida, sdkp->index); spin_unlock(&sd_index_lock);
+ /* + * 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);