{"id":"AZL-110735","summary":"CVE-2026-98942 affecting package kernel 6.6.157.1-1","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nsched_ext: Build the cid tables privately and publish them with RCU\n\nThe cid tables are visible to the cid kfuncs while being modified: the\nfirst enable publishes the global pointers before filling them,\nops.init_cids() overrides rewrite them in place, and re-enables rebuild\nthem in place. A racing TRACING or SYSCALL program can read unfilled\nentries, including uninitialized memory in the kmalloc'd tables, or torn\ntopo updates.\n\nTie the tables' lifetimes to the root sched instead: each root enable\nbuilds a fresh set privately and publishes the per-table __rcu globals once\nthe layout is final, and root disable unpublishes and RCU-frees the set. A\nnon-NULL global is now always a fully built table which stays valid for the\nreader's RCU read section, and lookups stay two loads. Kfuncs treat NULL as\nno-mapping, also after the scheduler exits instead of reporting the stale\nlast mapping.\n\nThe cid kfuncs are available whether the root scheduler is cid-form or\ncpu-form, the latter to allow gradual migration to cids. Every root\ntherefore builds and publishes a default mapping.\n\nEvery reader must either be gated on scheduler liveness or NULL-check\ninside an RCU read section. Fix the two kfuncs that were neither:\nscx_bpf_this_cid() read the table with no RCU or preemption protection and\nscx_bpf_task_cid() relied on KF_RCU, which doesn't put a sleepable program\nin an RCU read section. The hotplug callbacks are instead serialized by\nretiring the tables inside the cpus_read_lock() section that clears\nscx_root.\n\nv2: Document why every root builds the tables (desc + cid.c comment).","modified":"2026-10-25T05:30:37Z","published":"2026-10-23T13:17:15Z","upstream":["CVE-2026-98942"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98942"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"6.6.157.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-110735.json"}}],"schema_version":"1.9.0"}