CVE-2026-89775 is a vulnerability in Linux Kernel
Published on September 16, 2026
KVM: arm64: Handle negative S1 walk levels in VNCR TLB size evaluation
In the Linux kernel, the following vulnerability has been resolved:
KVM: arm64: Handle negative S1 walk levels in VNCR TLB size evaluation
Computing the effects of a TLB invalidation involves looking at
the size of the mapping cached by the TLB. For S1 mappings such as
VNCR, this is deducted from the combination of the base granule size
and the mapping level.
However, this implies that the S1 MMU is *on*. When the MMU is off,
we indicate this with the level being set to a "creative" value of
-127 (S1_MMU_DISABLED).
This ends-up being misinterpreted by pgshift_level_to_ttl() as it
doesn't handle negative levels at all (the level is immediately cast
to a u8 and only the bottom two bits considered), leading to an
invalidation size of 0. Not helpful.
Tidy-up pgshift_level_to_ttl() to handle these negative levels, and
ttl_to_size() to always return SZ_1G when no valid TTL is present.
This allows the removal of open-coded checks for similar situations.
Note that the check for a negative value not explicitely checking for
S1_MMU_DISABLED is deliberate, so that actual negative levels introduced
with LVA2 and D128 can take the same path if we ever support them.
Products Associated with CVE-2026-89775
Want to know whenever a new CVE is published for Linux Kernel? stack.watch will email you.
Affected Versions
Linux:- Version 7270cc9157f474dfc46750a34c9d7defc686b2eb and below be54a70067c7dbe1381157e8a238fa4b16ea9c05 is affected.
- Version 7270cc9157f474dfc46750a34c9d7defc686b2eb and below 1c9fca34b9625a67a7f1a03c8604f3df760c6c49 is affected.
- Version 7270cc9157f474dfc46750a34c9d7defc686b2eb and below 8053393680d4fa3eb962667d2be95dd39f0940e5 is affected.
- Version 6.16 is affected.
- Before 6.16 is unaffected.
- Version 6.18.51, <= 6.18.* is unaffected.
- Version 7.2.5, <= 7.2.* is unaffected.
- Version 7.3-rc1, <= * is unaffected.