[PATCH 2/2] drm/xe/queue: move xa_alloc to prevent UAF

[Matthew Auld]

On 23/09/2024 17:05, Matthew Brost wrote:
> On Mon, Sep 23, 2024 at 01:57:35PM +0100, Matthew Auld wrote:
>> Evil user can guess the next id of the queue before the ioctl completes
>> and then call queue destroy ioctl to trigger UAF since create ioctl is
>> still referencing the same queue. Move the xa_alloc all the way to the end
>> to prevent this.
>>
>> Fixes: 2149ded63079 ("drm/xe: Fix use after free when client stats are captured")
>> Signed-off-by: Matthew Auld <matthew.auld at intel.com>
>> Cc: Matthew Brost <matthew.brost at intel.com>
>> ---
>>   drivers/gpu/drm/xe/xe_exec_queue.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_exec_queue.c b/drivers/gpu/drm/xe/xe_exec_queue.c
>> index 7f28b7fc68d5..a1d4b9b0726e 100644
>> --- a/drivers/gpu/drm/xe/xe_exec_queue.c
>> +++ b/drivers/gpu/drm/xe/xe_exec_queue.c
>> @@ -635,6 +635,9 @@ int xe_exec_queue_create_ioctl(struct drm_device *dev, void *data,
>>   		}
>>   	}
>>   
>> +	q->xef = xe_file_get(xef);
> 
> Same comment as last patch, this looks coreect shall I merge my series
> and then you rebase?

Yeah, sounds fine.

> 
> Matt
> 
>> +
>> +	/* user id alloc must always be last in ioctl to prevent UAF */
>>   	mutex_lock(&xef->exec_queue.lock);
>>   	err = xa_alloc(&xef->exec_queue.xa, &id, q, xa_limit_32b, GFP_KERNEL);
>>   	mutex_unlock(&xef->exec_queue.lock);
>> @@ -642,7 +645,6 @@ int xe_exec_queue_create_ioctl(struct drm_device *dev, void *data,
>>   		goto kill_exec_queue;
>>   
>>   	args->exec_queue_id = id;
>> -	q->xef = xe_file_get(xef);
>>   
>>   	return 0;
>>   
>> -- 
>> 2.46.1
>>