block,scsi: verify return pointer from blk_get_request

The blk-core dead queue checks introduce an error scenario to
blk_get_request that returns NULL if the request queue has been
shutdown. This affects the behavior for __GFP_WAIT callers, who should
verify the return value before dereferencing.

Signed-off-by: Joe Lawrence <joe.lawrence@stratus.com>
Acked-by: Jiri Kosina <jkosina@suse.cz> [for pktdvd]
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
index 51bf5155ee75..29d056782833 100644
--- a/block/scsi_ioctl.c
+++ b/block/scsi_ioctl.c
@@ -448,6 +448,10 @@ int sg_scsi_ioctl(struct request_queue *q, struct gendisk *disk, fmode_t mode,
         }
 
         rq = blk_get_request(q, in_len ? WRITE : READ, __GFP_WAIT);
+        if (!rq) {
+                err = -ENODEV;
+                goto error_free_buffer;
+        }
 
         cmdlen = COMMAND_SIZE(opcode);
 
@@ -520,8 +524,9 @@ out:
         }
         
 error:
-        kfree(buffer);
         blk_put_request(rq);
+error_free_buffer:
+        kfree(buffer);
         return err;
 }
 EXPORT_SYMBOL_GPL(sg_scsi_ioctl);
@@ -534,6 +539,8 @@ static int __blk_send_generic(struct request_queue *q, struct gendisk *bd_disk,
         int err;
 
         rq = blk_get_request(q, WRITE, __GFP_WAIT);
+        if (!rq)
+                return -ENODEV;
         blk_rq_set_block_pc(rq);
         rq->timeout = BLK_DEFAULT_SG_TIMEOUT;
         rq->cmd[0] = cmd;