lkml.org 
[lkml]   [2012]   [Aug]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    SubjectRe: [PATCH] fix NULL-pointer dereference on scsi_run_queue
    On 08/04/12 22:36, Mike Christie wrote:
    > On 08/04/2012 03:18 PM, Bart Van Assche wrote:
    >> On 08/04/12 16:46, Mike Christie wrote:
    >>> I think we have to have scsi-ml do a get_device when a sdev is added to
    >>> the starved entry and then do a put_device when it is removed (must do
    >>> these under the host lock for the starved entry case too). I am not sure
    >>> if that is just a hack/papering-over of the problem and there are more
    >>> issues like this.
    >>
    >> That would result in a more complex patch than the patch at the start of
    >> this thread, isn't it ?
    >
    > Yaah, but the original patch in this thread is still racey isn't it?

    Indeed. How about the patch below ? Scsi devices are removed from
    starved_list after blk_cleanup_queue() and before put_device(). That
    guarantees that inside scsi_run_queue() get_device() under host lock
    will succeed.

    ---
    drivers/scsi/scsi_lib.c | 5 +++++
    drivers/scsi/scsi_sysfs.c | 7 ++++++-
    2 files changed, 11 insertions(+), 1 deletions(-)

    diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
    index ffd7773..bd7daec 100644
    --- a/drivers/scsi/scsi_lib.c
    +++ b/drivers/scsi/scsi_lib.c
    @@ -452,10 +452,15 @@ static void scsi_run_queue(struct request_queue *q)
    continue;
    }

    + get_device(&sdev->sdev_gendev);
    spin_unlock(shost->host_lock);
    +
    spin_lock(sdev->request_queue->queue_lock);
    __blk_run_queue(sdev->request_queue);
    spin_unlock(sdev->request_queue->queue_lock);
    +
    + put_device(&sdev->sdev_gendev);
    +
    spin_lock(shost->host_lock);
    }
    /* put any unprocessed entries back */
    diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
    index 093d4f6..44f232e 100644
    --- a/drivers/scsi/scsi_sysfs.c
    +++ b/drivers/scsi/scsi_sysfs.c
    @@ -348,7 +348,6 @@ static void scsi_device_dev_release_usercontext(struct work_struct *work)
    starget->reap_ref++;
    list_del(&sdev->siblings);
    list_del(&sdev->same_target_siblings);
    - list_del(&sdev->starved_entry);
    spin_unlock_irqrestore(sdev->host->host_lock, flags);

    cancel_work_sync(&sdev->event_work);
    @@ -956,6 +955,8 @@ int scsi_sysfs_add_sdev(struct scsi_device *sdev)
    void __scsi_remove_device(struct scsi_device *sdev)
    {
    struct device *dev = &sdev->sdev_gendev;
    + struct Scsi_Host *shost = sdev->host;
    + unsigned long flags;

    if (sdev->is_visible) {
    if (scsi_device_set_state(sdev, SDEV_CANCEL) != 0)
    @@ -977,6 +978,10 @@ void __scsi_remove_device(struct scsi_device *sdev)
    blk_cleanup_queue(sdev->request_queue);
    cancel_work_sync(&sdev->requeue_work);

    + spin_lock_irqsave(shost->host_lock, flags);
    + list_del(&sdev->starved_entry);
    + spin_unlock_irqrestore(shost->host_lock, flags);
    +
    if (sdev->host->hostt->slave_destroy)
    sdev->host->hostt->slave_destroy(sdev);
    transport_destroy_device(dev);
    --
    1.7.7



    \
     
     \ /
      Last update: 2012-08-06 20:21    [W:0.026 / U:1.112 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site