CVE-2026-45878

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() doesnt check for negative values so if watch_id is larger than INT_MAX it leads to a buffer overflow. (Negative shifts are undefined).

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);

–> 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().

Affected Software

References

• https://git.kernel.org/stable/c/2b36c0c1bcbbe15f6cfa9652084b3124c835a150
• https://git.kernel.org/stable/c/3c38a0f07aa2bfef2b219b1f045534ad93f85afd
• https://git.kernel.org/stable/c/5a19302cab5cec7ae7f1a60c619951e6c17d8742
• https://git.kernel.org/stable/c/971bf8e61e9b4abaacf9b35eaf76ec222758f9d6
• https://git.kernel.org/stable/c/a0d367e13db63a6ed76ee0d0a8c3a58c1fa98488