[ 03/23] SCSI: sd: fix crash when UA received on DIF enabled device

Greg Kroah-Hartman
2013-08-02T10:22:34Z

From: "Ewan D. Milne" <emilne@redhat.com>

commit 085b513f97d8d799d28491239be4b451bcd8c2c5 upstream.

sd_prep_fn will allocate a larger CDB for the command via mempool_alloc
for devices using DIF type 2 protection. This CDB was being freed
in sd_done, which results in a kernel crash if the command is retried
due to a UNIT ATTENTION. This change moves the code to free the larger
CDB into sd_unprep_fn instead, which is invoked after the request is
complete.

It is no longer necessary to call scsi_print_command separately for
this case as the ->cmnd will no longer be NULL in the normal code path.

Also removed conditional test for DIF type 2 when freeing the larger
CDB because the protection_type could have been changed via sysfs while
the command was executing.

Signed-off-by: Ewan D. Milne <emilne@redhat.com>
Acked-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/scsi/sd.c | 22 +++++++---------------
1 file changed, 7 insertions(+), 15 deletions(-)

--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -641,10 +641,17 @@ static int scsi_setup_flush_cmnd(struct

static void sd_unprep_fn(struct request_queue *q, struct request *rq)
{
+ struct scsi_cmnd *SCpnt = rq->special;
+
if (rq->cmd_flags & REQ_DISCARD) {
free_page((unsigned long)rq->buffer);
rq->buffer = NULL;
}
+ if (SCpnt->cmnd != rq->cmd) {
+ mempool_free(SCpnt->cmnd, sd_cdb_pool);
+ SCpnt->cmnd = NULL;
+ SCpnt->cmd_len = 0;
+ }
}

/**
@@ -1451,21 +1458,6 @@ static int sd_done(struct scsi_cmnd *SCp
if (rq_data_dir(SCpnt->request) == READ && scsi_prot_sg_count(SCpnt))
sd_dif_complete(SCpnt, good_bytes);

- if (scsi_host_dif_capable(sdkp->device->host, sdkp->protection_type)
- == SD_DIF_TYPE2_PROTECTION && SCpnt->cmnd != SCpnt->request->cmd) {
-
- /* We have to print a failed command here as the
- * extended CDB gets freed before scsi_io_completion()
- * is called.
- */
- if (result)
- scsi_print_command(SCpnt);
-
- mempool_free(SCpnt->cmnd, sd_cdb_pool);
- SCpnt->cmnd = NULL;
- SCpnt->cmd_len = 0;
- }
-
return good_bytes;
}