linux-kernel - Re: [PATCH] drm/ttm: add a check against null pointer dereference

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Message-ID: <e3232983-895d-b24c-2e25-bf874d8007b1@amd.com>
Date:   Wed, 14 Jul 2021 17:06:34 +0200
From:   Christian König <christian.koenig@....com>
To:     Zheyu Ma <zheyuma97@...il.com>, ray.huang@....com,
        airlied@...ux.ie, daniel@...ll.ch
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/ttm: add a check against null pointer dereference

Am 14.07.21 um 16:54 schrieb Zheyu Ma:
> When calling ttm_range_man_fini(), 'man' may be uninitialized, which may
> cause a null pointer dereference bug.
>
> Fix this by checking if it is a null pointer.

It would be better if the driver doesn't try to fini a manager which was 
never initialized, but for now that should work.

>
> This log reveals it:
>
> [    7.902580 ] BUG: kernel NULL pointer dereference, address: 0000000000000058
> [    7.905721 ] RIP: 0010:ttm_range_man_fini+0x40/0x160
> [    7.911826 ] Call Trace:
> [    7.911826 ]  radeon_ttm_fini+0x167/0x210
> [    7.911826 ]  radeon_bo_fini+0x15/0x40
> [    7.913767 ]  rs400_fini+0x55/0x80
> [    7.914358 ]  radeon_device_fini+0x3c/0x140
> [    7.914358 ]  radeon_driver_unload_kms+0x5c/0xe0
> [    7.914358 ]  radeon_driver_load_kms+0x13a/0x200
> [    7.914358 ]  ? radeon_driver_unload_kms+0xe0/0xe0
> [    7.914358 ]  drm_dev_register+0x1db/0x290
> [    7.914358 ]  radeon_pci_probe+0x16a/0x230
> [    7.914358 ]  local_pci_probe+0x4a/0xb0
>
> Signed-off-by: Zheyu Ma <zheyuma97@...il.com>

Reviewed-by: Christian König <christian.koenig@....com>

Going to push it later.

Thanks,
Christian.

> ---
>   drivers/gpu/drm/ttm/ttm_range_manager.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_range_manager.c b/drivers/gpu/drm/ttm/ttm_range_manager.c
> index 03395386e8a7..f4b08a8705b3 100644
> --- a/drivers/gpu/drm/ttm/ttm_range_manager.c
> +++ b/drivers/gpu/drm/ttm/ttm_range_manager.c
> @@ -181,6 +181,9 @@ int ttm_range_man_fini(struct ttm_device *bdev,
>   	struct drm_mm *mm = &rman->mm;
>   	int ret;
>   
> +	if (!man)
> +		return 0;
> +
>   	ttm_resource_manager_set_used(man, false);
>   
>   	ret = ttm_resource_manager_evict_all(bdev, man);