[PATCH 05/13] ide: Potential null pointer dereference in ide_raw_taskfile()

[Marina Makienko]

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/ide/ide-taskfile.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/drivers/ide/ide-taskfile.c b/drivers/ide/ide-taskfile.c
index 729428e..655d894 100644
--- a/drivers/ide/ide-taskfile.c
+++ b/drivers/ide/ide-taskfile.c
@@ -432,6 +432,10 @@ int ide_raw_taskfile(ide_drive_t *drive, struct ide_cmd *cmd, u8 *buf,
 	int rw = !(cmd->tf_flags & IDE_TFLAG_WRITE) ? READ : WRITE;
 
 	rq = blk_get_request(drive->queue, rw, __GFP_WAIT);
+
+	if (!rq)
+		return -EIO;
+
 	rq->cmd_type = REQ_TYPE_ATA_TASKFILE;
 
 	/*
-- 
1.7.7

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