In the Linux kernel, the following vulnerability has been resolved:
drm/amdkfd: Fix watch_id bounds checking in debug address watch v2
The address watch clear code receives watch_id as an unsigned value
(u32), but some helper functions were using a signed int and checked
bits by shifting with watch_id.
If a very large watch_id is passed from userspace, it can be converted
to a negative value. This can cause invalid shifts and may access
memory outside the watch_points array.
drm/amdkfd: Fix watch_id bounds checking in debug address watch v2
Fix this by checking that watch_id is within MAX_WATCH_ADDRESSES before
using it. Also use BIT(watch_id) to test and clear bits safely.
This keeps the behavior unchanged for valid watch IDs and avoids
undefined behavior for invalid ones.
Fixes the below:
drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_debug.c:448
kfd_dbg_trap_clear_dev_address_watch() error: buffer overflow
'pdd->watch_points' 4 <= u32max user_rl='0-3,2147483648-u32max' uncapped
drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_debug.c
433 int kfd_dbg_trap_clear_dev_address_watch(struct kfd_process_device *pdd,
434 uint32_t watch_id)
435 {
436 int r;
437
438 if (!kfd_dbg_owns_dev_watch_id(pdd, watch_id))
kfd_dbg_owns_dev_watch_id() doesn't check for negative values so if
watch_id is larger than INT_MAX it leads to a buffer overflow.
(Negative shifts are undefined).
<pre>
439 return -EINVAL;
440
441 if (!pdd->dev->kfd->shared_resources.enable_mes) {
442 r = debug_lock_and_unmap(pdd->dev->dqm);
443 if (r)
444 return r;
445 }
446
447 amdgpu_gfx_off_ctrl(pdd->dev->adev, false);
</pre>
--> 448 pdd->watch_points[watch_id] = pdd->dev->kfd2kgd->clear_address_watch(
449 pdd->dev->adev,
450 watch_id);
v2: (as per, Jonathan Kim)
- Add early watch_id >= MAX_WATCH_ADDRESSES validation in the set path to
match the clear path.
- Drop the redundant bounds check in kfd_dbg_owns_dev_watch_id().