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>

2 files changed, 4 insertions, 0 deletions

diff --git a/drivers/block/paride/pd.c b/drivers/block/paride/pd.c
index fea7e76a00de..ca831f741d89 100644
--- a/drivers/block/paride/pd.c
+++ b/drivers/block/paride/pd.c
@@ -722,6 +722,8 @@ static int pd_special_command(struct pd_unit *disk,
         int err = 0;
 
         rq = blk_get_request(disk->gd->queue, READ, __GFP_WAIT);
+        if (!rq)
+                return -ENODEV;
 
         rq->cmd_type = REQ_TYPE_SPECIAL;
         rq->special = func;
diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
index 758ac442c5b5..7fa8c80e8982 100644
--- a/drivers/block/pktcdvd.c
+++ b/drivers/block/pktcdvd.c
@@ -704,6 +704,8 @@ static int pkt_generic_packet(struct pktcdvd_device *pd, struct packet_command *
 
         rq = blk_get_request(q, (cgc->data_direction == CGC_DATA_WRITE) ?
                              WRITE : READ, __GFP_WAIT);
+        if (!rq)
+                return -ENODEV;
         blk_rq_set_block_pc(rq);
 
         if (cgc->buflen) {