[PATCH 1/2] drm/drv: Fix potential memory leak in drm_dev_init()

[Lyude Paul]

Reviewed-by: Lyude Paul <lyude at redhat.com>

Will go ahead and push these two upstream, thanks!

On Tue, 2022-11-01 at 15:07 +0800, Shang XiaoJing wrote:
> drm_dev_init() will add drm_dev_init_release() as a callback. When
> drmm_add_action() failed, the release function won't be added. As the
> result, the ref cnt added by device_get() in drm_dev_init() won't be put
> by drm_dev_init_release(), which leads to the memleak. Use
> drmm_add_action_or_reset() instead of drmm_add_action() to prevent
> memleak.
> 
> unreferenced object 0xffff88810bc0c800 (size 2048):
>   comm "modprobe", pid 8322, jiffies 4305809845 (age 15.292s)
>   hex dump (first 32 bytes):
>     e8 cc c0 0b 81 88 ff ff ff ff ff ff 00 00 00 00  ................
>     20 24 3c 0c 81 88 ff ff 18 c8 c0 0b 81 88 ff ff   $<.............
>   backtrace:
>     [<000000007251f72d>] __kmalloc+0x4b/0x1c0
>     [<0000000045f21f26>] platform_device_alloc+0x2d/0xe0
>     [<000000004452a479>] platform_device_register_full+0x24/0x1c0
>     [<0000000089f4ea61>] 0xffffffffa0736051
>     [<00000000235b2441>] do_one_initcall+0x7a/0x380
>     [<0000000001a4a177>] do_init_module+0x5c/0x230
>     [<000000002bf8a8e2>] load_module+0x227d/0x2420
>     [<00000000637d6d0a>] __do_sys_finit_module+0xd5/0x140
>     [<00000000c99fc324>] do_syscall_64+0x3f/0x90
>     [<000000004d85aa77>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> Fixes: 2cbf7fc6718b ("drm: Use drmm_ for drm_dev_init cleanup")
> Signed-off-by: Shang XiaoJing <shangxiaojing at huawei.com>
> ---
>  drivers/gpu/drm/drm_drv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index e3a1243dd2ae..b2c2a5872621 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -616,7 +616,7 @@ static int drm_dev_init(struct drm_device *dev,
>  	mutex_init(&dev->clientlist_mutex);
>  	mutex_init(&dev->master_mutex);
>  
> -	ret = drmm_add_action(dev, drm_dev_init_release, NULL);
> +	ret = drmm_add_action_or_reset(dev, drm_dev_init_release, NULL);
>  	if (ret)
>  		return ret;
>  

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat