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    Subject[PATCH 13/13] scsi: Potential null pointer dereference in scsi_eh_lock_door()
    Date
    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@ispras.ru>
    ---
    drivers/scsi/scsi_error.c | 3 +++
    1 files changed, 3 insertions(+), 0 deletions(-)

    diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
    index 4a6381c..7dd67d4 100644
    --- a/drivers/scsi/scsi_error.c
    +++ b/drivers/scsi/scsi_error.c
    @@ -1624,6 +1624,9 @@ static void scsi_eh_lock_door(struct scsi_device *sdev)
    */
    req = blk_get_request(sdev->request_queue, READ, GFP_KERNEL);

    + if (!req)
    + return;
    +
    req->cmd[0] = ALLOW_MEDIUM_REMOVAL;
    req->cmd[1] = 0;
    req->cmd[2] = 0;
    --
    1.7.7


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