On 10/13/2021 1:03 PM, Lang Yu wrote:
We should not dereference __user pointers directly.
https://yarchive.net/comp/linux/user_pointers.html
Fixes: 482f07775cf5
("drm/amdkfd: Simplify event ID and signal slot management")
Signed-off-by: Lang Yu <lang.yu@xxxxxxx>
---
drivers/gpu/drm/amd/amdkfd/kfd_events.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_events.c b/drivers/gpu/drm/amd/amdkfd/kfd_events.c
index 3eea4edee355..74d3bdcfe341 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_events.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_events.c
@@ -201,7 +201,7 @@ static int create_signal_event(struct file *devkfd,
p->signal_event_count++;
- ev->user_signal_address = &p->signal_page->user_address[ev->event_id];
This is interesting. I thought this wouldn't dereference.
See here -
https://en.cppreference.com/w/c/language/operator_member_access
"If the operand is an array index expression, no action is taken other
than the array-to-pointer conversion and the addition, so &a[N] is valid
for an array of size N (obtaining a pointer one past the end is okay,
dereferencing it is not, but dereference cancels out in this expression)"
Thanks,
Lijo
+ ev->user_signal_address = p->signal_page->user_address + ev->event_id;
pr_debug("Signal event number %zu created with id %d, address %p\n",
p->signal_event_count, ev->event_id,
ev->user_signal_address);
