CVE-2025-39895

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

sched: Fix sched_numa_find_nth_cpu() if mask offline

sched_numa_find_nth_cpu() uses a bsearch to look for the 'closest'

CPU in sched_domains_numa_masks and given cpus mask. However they

might not intersect if all CPUs in the cpus mask are offline. bsearch

will return NULL in that case, bail out instead of dereferencing a

bogus pointer.

The previous behaviour lead to this bug when using maxcpus=4 on an

rk3399 (LLLLbb) (i.e. booting with all big CPUs offline):

[ 1.422922] Unable to handle kernel paging request at virtual address ffffff8000000000

[ 1.423635] Mem abort info:

[ 1.423889] ESR = 0x0000000096000006

[ 1.424227] EC = 0x25: DABT (current EL), IL = 32 bits

[ 1.424715] SET = 0, FnV = 0

[ 1.424995] EA = 0, S1PTW = 0

[ 1.425279] FSC = 0x06: level 2 translation fault

[ 1.425735] Data abort info:

[ 1.425998] ISV = 0, ISS = 0x00000006, ISS2 = 0x00000000

[ 1.426499] CM = 0,

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References