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

[Christophe JAILLET]

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

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