[PATCH 01/13] block/paride: Potential null pointer dereference in pd_special_command()

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The function blk_get_request() can return NULL in some cases. There are
checks on it if function is called with argumetns one of which is
GFP_ATOMIC/GFP_NOIO/etc. If system couldn't find request
blk_get_request() return NULL.

But if there is function call with argument __GFP_WAIT
the system will wait until get request or the queue becomes
dead. If something kills the queue, blk_get_request()
return NULL and next operations will lead to errors.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Marina Makienko <makienko@xxxxxxxxx>
---
 drivers/block/paride/pd.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/drivers/block/paride/pd.c b/drivers/block/paride/pd.c
index 831e3ac..6e28910 100644
--- a/drivers/block/paride/pd.c
+++ b/drivers/block/paride/pd.c
@@ -723,6 +723,9 @@ static int pd_special_command(struct pd_unit *disk,
 
 	rq = blk_get_request(disk->gd->queue, READ, __GFP_WAIT);
 
+	if (!rq)
+		return Fail;
+
 	rq->cmd_type = REQ_TYPE_SPECIAL;
 	rq->special = func;
 
-- 
1.7.7

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