[PATCH 1/2] drm/vkms: Fix memory leak in vkms_init()

[Melissa Wen]

On 11/01, Yuan Can wrote:
> A memory leak was reported after the vkms module install failed.
> 
> unreferenced object 0xffff88810bc28520 (size 16):
>   comm "modprobe", pid 9662, jiffies 4298009455 (age 42.590s)
>   hex dump (first 16 bytes):
>     01 01 00 64 81 88 ff ff 00 00 dc 0a 81 88 ff ff  ...d............
>   backtrace:
>     [<00000000e7561ff8>] kmalloc_trace+0x27/0x60
>     [<000000000b1954a0>] 0xffffffffc45200a9
>     [<00000000abbf1da0>] do_one_initcall+0xd0/0x4f0
>     [<000000001505ee87>] do_init_module+0x1a4/0x680
>     [<00000000958079ad>] load_module+0x6249/0x7110
>     [<00000000117e4696>] __do_sys_finit_module+0x140/0x200
>     [<00000000f74b12d2>] do_syscall_64+0x35/0x80
>     [<000000008fc6fcde>] entry_SYSCALL_64_after_hwframe+0x46/0xb0
> 
> The reason is that the vkms_init() returns without checking the return
> value of vkms_create(), and if the vkms_create() failed, the config
> allocated at the beginning of vkms_init() is leaked.
> 
>  vkms_init()
>    config = kmalloc(...) # config allocated
>    ...
>    return vkms_create() # vkms_create failed and config is leaked
> 
> Fix this problem by checking return value of vkms_create() and free the
> config if error happened.
> 
> Fixes: 2df7af93fdad ("drm/vkms: Add vkms_config type")
> Signed-off-by: Yuan Can <yuancan at huawei.com>
> ---
>  drivers/gpu/drm/vkms/vkms_drv.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
> index 0ffe5f0e33f7..dfe983eaa07f 100644
> --- a/drivers/gpu/drm/vkms/vkms_drv.c
> +++ b/drivers/gpu/drm/vkms/vkms_drv.c
> @@ -218,6 +218,7 @@ static int vkms_create(struct vkms_config *config)
>  
>  static int __init vkms_init(void)
>  {
> +	int ret;
>  	struct vkms_config *config;
>  
>  	config = kmalloc(sizeof(*config), GFP_KERNEL);
> @@ -230,7 +231,11 @@ static int __init vkms_init(void)
>  	config->writeback = enable_writeback;
>  	config->overlay = enable_overlay;
>  
> -	return vkms_create(config);
> +	ret = vkms_create(config);
> +	if (ret)
> +		kfree(config);
> +
> +	return ret;

Good catch. Thanks,

Reviewed-by: Melissa Wen <mwen at igalia.com>

>  }
>  
>  static void vkms_destroy(struct vkms_config *config)
> -- 
> 2.17.1
> 
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