Re: [PATCH] drm/amdkfd: Fix an illegal memory access

[Qu Huang]

On 2023/2/22 3:17, Christophe JAILLET wrote:
> Le 21/02/2023 à 17:26, Felix Kuehling a écrit :
>>
>> On 2023-02-21 06:35, qu.huang-fxUVXftIFDnyG1zEObXtfA@xxxxxxxxxxxxxxxx wrote:
>>> From: Qu Huang <qu.huang-fxUVXftIFDnyG1zEObXtfA@xxxxxxxxxxxxxxxx>
>>>
>>> In the kfd_wait_on_events() function, the kfd_event_waiter structure is
>>> allocated by alloc_event_waiters(), but the event field of the waiter
>>> structure is not initialized; When copy_from_user() fails in the
>>> kfd_wait_on_events() function, it will enter exception handling to
>>> release the previously allocated memory of the waiter structure;
>>> Due to the event field of the waiters structure being accessed
>>> in the free_waiters() function, this results in illegal memory access
>>> and system crash, here is the crash log:
>>>
>>> localhost kernel: RIP: 0010:native_queued_spin_lock_slowpath+0x185/0x1e0
>>> localhost kernel: RSP: 0018:ffffaa53c362bd60 EFLAGS: 00010082
>>> localhost kernel: RAX: ff3d3d6bff4007cb RBX: 0000000000000282 RCX: 00000000002c0000
>>> localhost kernel: RDX: ffff9e855eeacb80 RSI: 000000000000279c RDI: ffffe7088f6a21d0
>>> localhost kernel: RBP: ffffe7088f6a21d0 R08: 00000000002c0000 R09: ffffaa53c362be64
>>> localhost kernel: R10: ffffaa53c362bbd8 R11: 0000000000000001 R12: 0000000000000002
>>> localhost kernel: R13: ffff9e7ead15d600 R14: 0000000000000000 R15: ffff9e7ead15d698
>>> localhost kernel: FS:  0000152a3d111700(0000) GS:ffff9e855ee80000(0000) knlGS:0000000000000000
>>> localhost kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>> localhost kernel: CR2: 0000152938000010 CR3: 000000044d7a4000 CR4: 00000000003506e0
>>> localhost kernel: Call Trace:
>>> localhost kernel: _raw_spin_lock_irqsave+0x30/0x40
>>> localhost kernel: remove_wait_queue+0x12/0x50
>>> localhost kernel: kfd_wait_on_events+0x1b6/0x490 [hydcu]
>>> localhost kernel: ? ftrace_graph_caller+0xa0/0xa0
>>> localhost kernel: kfd_ioctl+0x38c/0x4a0 [hydcu]
>>> localhost kernel: ? kfd_ioctl_set_trap_handler+0x70/0x70 [hydcu]
>>> localhost kernel: ? kfd_ioctl_create_queue+0x5a0/0x5a0 [hydcu]
>>> localhost kernel: ? ftrace_graph_caller+0xa0/0xa0
>>> localhost kernel: __x64_sys_ioctl+0x8e/0xd0
>>> localhost kernel: ? syscall_trace_enter.isra.18+0x143/0x1b0
>>> localhost kernel: do_syscall_64+0x33/0x80
>>> localhost kernel: entry_SYSCALL_64_after_hwframe+0x44/0xa9
>>> localhost kernel: RIP: 0033:0x152a4dff68d7
>>>
>>> Signed-off-by: Qu Huang <qu.huang-fxUVXftIFDnyG1zEObXtfA@xxxxxxxxxxxxxxxx>
>>> ---
>>>   drivers/gpu/drm/amd/amdkfd/kfd_events.c | 1 +
>>>   1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_events.c b/drivers/gpu/drm/amd/amdkfd/kfd_events.c
>>> index 729d26d..e5faaad 100644
>>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_events.c
>>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_events.c
>>> @@ -787,6 +787,7 @@ static struct kfd_event_waiter *alloc_event_waiters(uint32_t num_events)
>>>       for (i = 0; (event_waiters) && (i < num_events) ; i++) {
>>>           init_wait(&event_waiters[i].wait);
>>>           event_waiters[i].activated = false;
>>> +        event_waiters[i].event = NULL;
>>
>> Thank you for catching this. We're often lazy about initializing things to NULL or 0 because most of our data structures are allocated with kzalloc or similar. I'm not sure why we're not doing this here. If we allocated event_waiters with kcalloc, we could also remove the initialization of activated. I think that would be the cleaner and safer solution.
>
> Hi,
>
> I think that the '(event_waiters) &&' in the 'for' can also be removed.
> 'event_waiters' is already NULL tested a few lines above
>
>
> Just my 2c.
>
> CJ
>

Thanks for the suggestions from Felix and CJ, I have re-submitted patch v2, please review it：

https://lore.kernel.org/all/ea5b997309825b21e406f9bad2ce8779@xxxxxxxxx/

Regards,

Qu


>>
>> Regards,
>>    Felix
>>
>>
>>>       }
>>>
>>>       return event_waiters;
>>> -- 
>>> 1.8.3.1
>>
>