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Mon, 13 Oct 2025 13:18:11 +0000 Message-ID: <8ec09842-563e-4879-b505-bd82ea87bae6@amd.com> Date: Mon, 13 Oct 2025 15:18:07 +0200 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] drm/ttm: Add safety check for NULL man->bdev in ttm_resource_manager_usage To: "Jesse.Zhang" , amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Cc: Alexander.Deucher@amd.com, Lijo Lazar , "Paneer Selvam, Arunpravin" References: <20251013085849.1735612-1-Jesse.Zhang@amd.com> Content-Language: en-US From: =?UTF-8?Q?Christian_K=C3=B6nig?= In-Reply-To: <20251013085849.1735612-1-Jesse.Zhang@amd.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-ClientProxiedBy: BN1PR12CA0020.namprd12.prod.outlook.com (2603:10b6:408:e1::25) To PH7PR12MB5685.namprd12.prod.outlook.com (2603:10b6:510:13c::22) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH7PR12MB5685:EE_|BL3PR12MB6378:EE_ X-MS-Office365-Filtering-Correlation-Id: 808d2a53-2154-4814-38ad-08de0a5af521 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|1800799024|366016; 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This leads to a NULL pointer dereference when attempting to acquire the `lru_lock`, triggering kernel OOPS. > > Fix this by adding an explicit safety check for `man->bdev` before accessing its members: > - Use `WARN_ON_ONCE(!man->bdev)` to emit a one-time warning (a soft assertion) when `man->bdev` is NULL. This helps catch invalid usage patterns during debugging without breaking production workflows. > - Return 0 immediately if `man->bdev` is NULL, as a non-initialized manager cannot have valid resource usage to report. > > Suggested-by: Christian König > Suggested-by: Lijo Lazar > Signed-off-by: Jesse Zhang Reviewed-by: Christian König @Arun could you push this one to drm-misc-next if nobody objects? Thanks in advance, Christian > --- > drivers/gpu/drm/ttm/ttm_resource.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/gpu/drm/ttm/ttm_resource.c b/drivers/gpu/drm/ttm/ttm_resource.c > index e2c82ad07eb4..d93d1bef6768 100644 > --- a/drivers/gpu/drm/ttm/ttm_resource.c > +++ b/drivers/gpu/drm/ttm/ttm_resource.c > @@ -587,6 +587,9 @@ uint64_t ttm_resource_manager_usage(struct ttm_resource_manager *man) > { > uint64_t usage; > > + if (WARN_ON_ONCE(!man->bdev)) > + return 0; > + > spin_lock(&man->bdev->lru_lock); > usage = man->usage; > spin_unlock(&man->bdev->lru_lock);