Re: [PATCH v2] drm/xe: Fix possible UAF in guc_exec_queue_process_msg

["Ghimiray, Himal Prasad" <himal.prasad.ghimiray@intel.com>]

On 24-07-2024 21:12, Upadhyay, Tejas wrote:
> 
> 
>> -----Original Message-----
>> From: Intel-xe <intel-xe-bounces@lists.freedesktop.org> On Behalf Of
>> Matthew Brost
>> Sent: Wednesday, July 24, 2024 12:49 AM
>> To: intel-xe@lists.freedesktop.org
>> Cc: dan.carpenter@linaro.org
>> Subject: [PATCH v2] drm/xe: Fix possible UAF in
>> guc_exec_queue_process_msg
>>
>> Store xe_device ahead of processing message as message can be free'd in
>> some cases.
>>
>> v2:
>>   - Including missing local changes
>>
>> Reported-by: kernel test robot <lkp@intel.com>
>> Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
>> Closes: https://lore.kernel.org/r/202407231445.rpisd1vA-lkp@intel.com/
>> Fixes: d930c19fdff3 ("drm/xe: Build PM into GuC CT layer")
>> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
>> ---
>>   drivers/gpu/drm/xe/xe_guc_submit.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_guc_submit.c
>> b/drivers/gpu/drm/xe/xe_guc_submit.c
>> index da2ead86b9ae..b8f938539a90 100644
>> --- a/drivers/gpu/drm/xe/xe_guc_submit.c
>> +++ b/drivers/gpu/drm/xe/xe_guc_submit.c
>> @@ -1395,6 +1395,8 @@ static void
>> __guc_exec_queue_process_msg_resume(struct xe_sched_msg *msg)
>>
>>   static void guc_exec_queue_process_msg(struct xe_sched_msg *msg)  {
>> +	struct xe_device *xe =
>> +guc_to_xe(exec_queue_to_guc(msg->private_data));
> 
> If msg freed at this point, don't you need to protect against NULL, just in case?
> 
> Thanks,
> Tejas

xe_sched_process_msg_work the caller of the ops ensures the routine is 
called only if msg is valid.

Below msg->opcode for eg like CLEANUP can clean it uo.

>> +
>>   	trace_xe_sched_msg_recv(msg);
>>
>>   	switch (msg->opcode) {
>> @@ -1414,7 +1416,7 @@ static void guc_exec_queue_process_msg(struct
>> xe_sched_msg *msg)
>>   		XE_WARN_ON("Unknown message type");
>>   	}
>>
>> -	xe_pm_runtime_put(guc_to_xe(exec_queue_to_guc(msg-
>>> private_data)));
>> +	xe_pm_runtime_put(xe);
>>   }
>>
>>   static const struct drm_sched_backend_ops drm_sched_ops = {
>> --
>> 2.34.1
>