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Subject[ 013/109] SCSI: Fix device removal NULL pointer dereference
Date
From: Greg KH <gregkh@linuxfoundation.org>

3.4-stable review patch. If anyone has any objections, please let me know.

------------------

From: Bart Van Assche <bvanassche@acm.org>

commit 67bd94130015c507011af37858989b199c52e1de upstream.

Use blk_queue_dead() to test whether the queue is dead instead
of !sdev. Since scsi_prep_fn() may be invoked concurrently with
__scsi_remove_device(), keep the queuedata (sdev) pointer in
__scsi_remove_device(). This patch fixes a kernel oops that
can be triggered by USB device removal. See also
http://www.spinics.net/lists/linux-scsi/msg56254.html.

Other changes included in this patch:
- Swap the blk_cleanup_queue() and kfree() calls in
scsi_host_dev_release() to make that code easier to grasp.
- Remove the queue dead check from scsi_run_queue() since the
queue state can change anyway at any point in that function
where the queue lock is not held.
- Remove the queue dead check from the start of scsi_request_fn()
since it is redundant with the scsi_device_online() check.

Reported-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Reviewed-by: Tejun Heo <tj@kernel.org>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/scsi/hosts.c | 7 ++++---
drivers/scsi/scsi_lib.c | 32 ++++----------------------------
drivers/scsi/scsi_priv.h | 1 -
drivers/scsi/scsi_sysfs.c | 5 +----
4 files changed, 9 insertions(+), 36 deletions(-)

--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -290,6 +290,7 @@ static void scsi_host_dev_release(struct
struct Scsi_Host *shost = dev_to_shost(dev);
struct device *parent = dev->parent;
struct request_queue *q;
+ void *queuedata;

scsi_proc_hostdir_rm(shost->hostt);

@@ -299,9 +300,9 @@ static void scsi_host_dev_release(struct
destroy_workqueue(shost->work_q);
q = shost->uspace_req_q;
if (q) {
- kfree(q->queuedata);
- q->queuedata = NULL;
- scsi_free_queue(q);
+ queuedata = q->queuedata;
+ blk_cleanup_queue(q);
+ kfree(queuedata);
}

scsi_destroy_command_freelist(shost);
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -406,10 +406,6 @@ static void scsi_run_queue(struct reques
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);
@@ -1370,16 +1366,16 @@ static inline int scsi_host_queue_ready(
* may be changed after request stacking drivers call the function,
* regardless of taking lock or not.
*
- * When scsi can't dispatch I/Os anymore and needs to kill I/Os
- * (e.g. !sdev), scsi needs to return 'not busy'.
- * Otherwise, request stacking drivers may hold requests forever.
+ * When scsi can't dispatch I/Os anymore and needs to kill I/Os scsi
+ * needs to return 'not busy'. Otherwise, request stacking drivers
+ * may hold requests forever.
*/
static int scsi_lld_busy(struct request_queue *q)
{
struct scsi_device *sdev = q->queuedata;
struct Scsi_Host *shost;

- if (!sdev)
+ if (blk_queue_dead(q))
return 0;

shost = sdev->host;
@@ -1490,12 +1486,6 @@ static void scsi_request_fn(struct reque
struct scsi_cmnd *cmd;
struct request *req;

- if (!sdev) {
- while ((req = blk_peek_request(q)) != NULL)
- scsi_kill_request(req, q);
- return;
- }
-
if(!get_device(&sdev->sdev_gendev))
/* We must be tearing the block queue down already */
return;
@@ -1697,20 +1687,6 @@ struct request_queue *scsi_alloc_queue(s
return q;
}

-void scsi_free_queue(struct request_queue *q)
-{
- unsigned long flags;
-
- WARN_ON(q->queuedata);
-
- /* cause scsi_request_fn() to kill all non-finished requests */
- spin_lock_irqsave(q->queue_lock, flags);
- q->request_fn(q);
- spin_unlock_irqrestore(q->queue_lock, flags);
-
- blk_cleanup_queue(q);
-}
-
/*
* Function: scsi_block_requests()
*
--- a/drivers/scsi/scsi_priv.h
+++ b/drivers/scsi/scsi_priv.h
@@ -84,7 +84,6 @@ extern void scsi_next_command(struct scs
extern void scsi_io_completion(struct scsi_cmnd *, unsigned int);
extern void scsi_run_host_queues(struct Scsi_Host *shost);
extern struct request_queue *scsi_alloc_queue(struct scsi_device *sdev);
-extern void scsi_free_queue(struct request_queue *q);
extern int scsi_init_queue(void);
extern void scsi_exit_queue(void);
struct request_queue;
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -971,11 +971,8 @@ void __scsi_remove_device(struct scsi_de
sdev->host->hostt->slave_destroy(sdev);
transport_destroy_device(dev);

- /* cause the request function to reject all I/O requests */
- sdev->request_queue->queuedata = NULL;
-
/* Freeing the queue signals to block that we're done */
- scsi_free_queue(sdev->request_queue);
+ blk_cleanup_queue(sdev->request_queue);
put_device(dev);
}




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