[PATCH libdrm v2] etnaviv: prevent deadlock in error path

[Eric Engestrom]

On Monday, 2017-08-21 14:42:51 +0200, Philipp Zabel wrote:
> If drmPrimeFDToHandle fails in etna_bo_from_dmabuf, the function must
> not return with the table_lock mutex held. There is no reason to call
> drmPrimeFDToHandle under that lock, so just take the lock after trying
> to obtain the handle.
> 
> Based on ceb70a6b1015 ("freedreno: prevent deadlock in error path").
> 
> Signed-off-by: Philipp Zabel <p.zabel at pengutronix.de>

Reviewed-by: Eric Engestrom <eric.engestrom at imgtec.com>

> ---
> v2: keep lock around drmPrimeFDToHandle call
> ---
>  etnaviv/etnaviv_bo.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/etnaviv/etnaviv_bo.c b/etnaviv/etnaviv_bo.c
> index 0cc3ab97..86fb894b 100644
> --- a/etnaviv/etnaviv_bo.c
> +++ b/etnaviv/etnaviv_bo.c
> @@ -225,10 +225,15 @@ struct etna_bo *etna_bo_from_dmabuf(struct etna_device *dev, int fd)
>  	int ret, size;
>  	uint32_t handle;
>  
> +	/* take the lock before calling drmPrimeFDToHandle to avoid
> +	 * racing against etna_bo_del, which might invalidate the
> +	 * returned handle.
> +	 */
>  	pthread_mutex_lock(&table_lock);
>  
>  	ret = drmPrimeFDToHandle(dev->fd, fd, &handle);
>  	if (ret) {
> +		pthread_mutex_unlock(&table_lock);
>  		return NULL;
>  	}
>  
> -- 
> 2.11.0
>