CVE-2026-98546arm64/boot: Disable trapping of PMZR_EL0 writes to EL2

Official description

In the Linux kernel, the following vulnerability has been resolved: arm64/boot: Disable trapping of PMZR_EL0 writes to EL2 __init_el2_fgt2() writes one mask to both HDFGRTR2_EL2 and HDFGWTR2_EL2. PMZR_EL0 is write-only, so its trap bit, nPMZR_EL0, exists only in HDFGWTR2_EL2 and is therefore never set: a PMZR_EL0 write from the host traps to EL2, where the nVHE hypervisor has no handler and BUG()s. The kernel never writes PMZR_EL0, but kernel.perf_user_access=1 has the PMU driver set PMUSERENR_EL0.UEN for a task with a user-read event, so a write from EL0 reaches the trap and takes the host down without a panic message. Accumulate the HDFGWTR2_EL2 bits separately, as __init_el2_fgt() already does for HDFGWTR_EL2, and set nPMZR_EL0 with the other FEAT_PMUv3p9 bits.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/bb8c90c86441c090e9036f019cf1b4d7894a2c40
• https://git.kernel.org/stable/c/071f51188a5d8ec10535541255587976d12fc7d8
• https://git.kernel.org/stable/c/ce71865bf43f88bed9d9218e9218e537150be506
• https://git.kernel.org/stable/c/2bc6b218717b9d08f466f88209251d54bc09b207