diff mbox

dvb: siano: free spinlock before schedule()

Message ID 1280256161-7971-1-git-send-email-segooon@gmail.com (mailing list archive)
State Superseded, archived
Headers

Commit Message

Kulikov Vasiliy July 27, 2010, 6:42 p.m. UTC 
  Calling schedule() holding spinlock with disables irqs is improper. As
spinlock protects list coredev->buffers, it can be unlocked untill wakeup.
This bug was introduced in a9349315f65cd6a16e8fab1f6cf0fd40f379c4db.

Signed-off-by: Kulikov Vasiliy <segooon@gmail.com>
---
 drivers/media/dvb/siano/smscoreapi.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

Comments

Jiri Slaby July 27, 2010, 10:24 p.m. UTC | #1 
On 07/27/2010 08:42 PM, Kulikov Vasiliy wrote:
> Calling schedule() holding spinlock with disables irqs is improper. As
> spinlock protects list coredev->buffers, it can be unlocked untill wakeup.
> This bug was introduced in a9349315f65cd6a16e8fab1f6cf0fd40f379c4db.
> 
> Signed-off-by: Kulikov Vasiliy <segooon@gmail.com>
> ---
>  drivers/media/dvb/siano/smscoreapi.c |    6 ++++--
>  1 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/dvb/siano/smscoreapi.c b/drivers/media/dvb/siano/smscoreapi.c
> index 7f2c94a..d93468c 100644
> --- a/drivers/media/dvb/siano/smscoreapi.c
> +++ b/drivers/media/dvb/siano/smscoreapi.c
> @@ -1113,9 +1113,11 @@ struct smscore_buffer_t *smscore_getbuffer(struct smscore_device_t *coredev)
>  	 */
>  
>  	prepare_to_wait(&coredev->buffer_mng_waitq, &wait, TASK_INTERRUPTIBLE);
> -
> -	if (list_empty(&coredev->buffers))
> +	if (list_empty(&coredev->buffers)) {
> +		spin_unlock_irqrestore(&coredev->bufferslock, flags);
>  		schedule();
> +		spin_lock_irqsave(&coredev->bufferslock, flags);
> +	}
>  
>  	finish_wait(&coredev->buffer_mng_waitq, &wait);

There is a better fix (which fixes the potential NULL dereference):
http://lkml.org/lkml/2010/6/7/175

Richard, could you address the comments there and resend?

regards,
diff mbox

Patch

diff --git a/drivers/media/dvb/siano/smscoreapi.c b/drivers/media/dvb/siano/smscoreapi.c
index 7f2c94a..d93468c 100644
--- a/drivers/media/dvb/siano/smscoreapi.c
+++ b/drivers/media/dvb/siano/smscoreapi.c
@@ -1113,9 +1113,11 @@  struct smscore_buffer_t *smscore_getbuffer(struct smscore_device_t *coredev)
 	 */
 
 	prepare_to_wait(&coredev->buffer_mng_waitq, &wait, TASK_INTERRUPTIBLE);
-
-	if (list_empty(&coredev->buffers))
+	if (list_empty(&coredev->buffers)) {
+		spin_unlock_irqrestore(&coredev->bufferslock, flags);
 		schedule();
+		spin_lock_irqsave(&coredev->bufferslock, flags);
+	}
 
 	finish_wait(&coredev->buffer_mng_waitq, &wait);