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    Subject[34-longterm 169/196] fix oops in scsi_run_queue()
    Date
    From: James Bottomley <James.Bottomley@suse.de>

    -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    If you see a problem with using this for longterm, please comment.
    -------------------

    commit c055f5b2614b4f758ae6cc86733f31fa4c2c5844 upstream.

    The recent commit closing the race window in device teardown:

    commit 86cbfb5607d4b81b1a993ff689bbd2addd5d3a9b
    Author: James Bottomley <James.Bottomley@suse.de>
    Date: Fri Apr 22 10:39:59 2011 -0500

    [SCSI] put stricter guards on queue dead checks

    is causing a potential NULL deref in scsi_run_queue() because the
    q->queuedata may already be NULL by the time this function is called.
    Since we shouldn't be running a queue that is being torn down, simply
    add a NULL check in scsi_run_queue() to forestall this.

    Tested-by: Jim Schutt <jaschut@sandia.gov>
    Signed-off-by: James Bottomley <James.Bottomley@suse.de>
    Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
    ---
    drivers/scsi/scsi_lib.c | 7 ++++++-
    1 file changed, 6 insertions(+), 1 deletion(-)

    diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
    index c2a9e12..725f3cd 100644
    --- a/drivers/scsi/scsi_lib.c
    +++ b/drivers/scsi/scsi_lib.c
    @@ -400,10 +400,15 @@ static inline int scsi_host_is_busy(struct Scsi_Host *shost)
    static void scsi_run_queue(struct request_queue *q)
    {
    struct scsi_device *sdev = q->queuedata;
    - struct Scsi_Host *shost = sdev->host;
    + struct Scsi_Host *shost;
    LIST_HEAD(starved_list);
    unsigned long flags;

    + /* if the device is dead, sdev will be NULL, so no queue to run */
    + if (!sdev)
    + return;
    +
    + shost = sdev->host;
    if (scsi_target(sdev)->single_lun)
    scsi_single_lun_run(sdev);

    --
    1.7.9.3


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