{"id":"CVE-2026-90211","summary":"bpf, s390: Clear fetch destination on faulting arena atomic","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf, s390: Clear fetch destination on faulting arena atomic\n\nSame missing register clear as on riscv64. A RMW atomic on an arena pointer\nis converted to BPF_PROBE_ATOMIC and gets an exception table entry, but\nbpf_jit_probe_atomic_pre() only fills in the arena base and the probe\noffset, leaving probe-\u003ereg at the -1 that bpf_jit_probe_init() set, which\nbpf_jit_probe_post() writes into the entry and ex_handler_bpf() then reads\nback as \"there is nothing to clear\".\n\nThat is right for a plain BPF_{ADD,AND,OR,XOR}, which only writes memory,\nbut an RMW carrying BPF_FETCH also reads the old value into a register:\nsrc_reg for BPF_{ADD,AND,OR,XOR} | BPF_FETCH and BPF_XCHG, and r0 for\nBPF_CMPXCHG. So on a fault over an unmapped arena page the program resumes\nat the landing pad with whatever that register held before the atomic\ninstead of the 0 that every other BPF_PROBE_* access delivers.\n\nFill probe-\u003ereg in from bpf_atomic_load_reg(). Unlike x86-64 and arm64,\ns390x does not report arena violations from its exception handler, so there\nis no access direction to correct here, only the missing register clear.","modified":"2026-09-19T03:47:25.414242836Z","published":"2026-09-17T16:07:25.454Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90211.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/1a26541b3f60ce447433a4c4dd56edb10d2cd580"},{"type":"WEB","url":"https://git.kernel.org/stable/c/44b702fceb4cf3a4ddbfb496f487b034814bf1a3"},{"type":"WEB","url":"https://git.kernel.org/stable/c/cc3e12330599f097f0e1f792435686ddc276f26d"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90211.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-90211"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"2f9469484a3b52c66b799de73bd1ca75617bc8d5"},{"fixed":"1a26541b3f60ce447433a4c4dd56edb10d2cd580"},{"fixed":"44b702fceb4cf3a4ddbfb496f487b034814bf1a3"},{"fixed":"cc3e12330599f097f0e1f792435686ddc276f26d"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90211.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.11.0"},{"fixed":"6.12.110"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"7.2.6"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90211.json"}}],"schema_version":"1.9.0"}