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:
- 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.
- 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.
- If IDLE_WAIT_TIME reads back as 0, maxcnt evaluates to 0 and
the maxcnt - 1 clamp wraps to 0xFFFFFFFF in u32.
- 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 the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
- EG Severity
- Not assessed: no CVSS publishedA missing CVSS is not a severity of zero.
- EG Likelihood
- 0.2% within 30 daysSource: FIRST EPSS. FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- No SSVC decision: EchelonGraph has not assessed this CVECISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the BOD 26-04 block below.
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it