{"id":"CVE-2026-52980","summary":"sched/fair: Clear rel_deadline when initializing forked entities","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nsched/fair: Clear rel_deadline when initializing forked entities\n\nA yield-triggered crash can happen when a newly forked sched_entity\nenters the fair class with se-\u003erel_deadline unexpectedly set.\n\nThe failing sequence is:\n\n  1. A task is forked while se-\u003erel_deadline is still set.\n  2. __sched_fork() initializes vruntime, vlag and other sched_entity\n     state, but does not clear rel_deadline.\n  3. On the first enqueue, enqueue_entity() calls place_entity().\n  4. Because se-\u003erel_deadline is set, place_entity() treats se-\u003edeadline\n     as a relative deadline and converts it to an absolute deadline by\n     adding the current vruntime.\n  5. However, the forked entity's deadline is not a valid inherited\n     relative deadline for this new scheduling instance, so the conversion\n     produces an abnormally large deadline.\n  6. If the task later calls sched_yield(), yield_task_fair() advances\n     se-\u003evruntime to se-\u003edeadline.\n  7. The inflated vruntime is then used by the following enqueue path,\n     where the vruntime-derived key can overflow when multiplied by the\n     entity weight.\n  8. This corrupts cfs_rq-\u003esum_w_vruntime, breaks EEVDF eligibility\n     calculation, and can eventually make all entities appear ineligible.\n     pick_next_entity() may then return NULL unexpectedly, leading to a\n     later NULL dereference.\n\nA captured trace shows the effect clearly. Before yield, the entity's\nvruntime was around:\n\n  9834017729983308\n\nAfter yield_task_fair() executed:\n\n  se-\u003evruntime = se-\u003edeadline\n\nthe vruntime jumped to:\n\n  19668035460670230\n\nand the deadline was later advanced further to:\n\n  19668035463470230\n\nThis shows that the deadline had already become abnormally large before\nyield_task_fair() copied it into vruntime.\n\nrel_deadline is only meaningful when se-\u003edeadline really carries a\nrelative deadline that still needs to be placed against vruntime. A\nfreshly forked sched_entity should not inherit or retain this state.\nClear se-\u003erel_deadline in __sched_fork(), together with the other\nsched_entity runtime state, so that the first enqueue does not interpret\nthe new entity's deadline as a stale relative deadline.","modified":"2026-07-08T08:13:44.921536835Z","published":"2026-06-24T16:28:56.457Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/52xxx/CVE-2026-52980.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/3da56dc063cd77b9c0b40add930767fab4e389f3"},{"type":"WEB","url":"https://git.kernel.org/stable/c/8f4a16200785f49cf02c5b71bdfe7a9dab63f23a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c71bf35caba12bfd9bc23e32b0bcd9e02d1cf1ac"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f3c16e1f4a314a20717ab90a41885f8111a242ab"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/52xxx/CVE-2026-52980.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-52980"},{"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":"82e9d0456e06cebe2c89f3c73cdbc9e3805e9437"},{"fixed":"c71bf35caba12bfd9bc23e32b0bcd9e02d1cf1ac"},{"fixed":"f3c16e1f4a314a20717ab90a41885f8111a242ab"},{"fixed":"8f4a16200785f49cf02c5b71bdfe7a9dab63f23a"},{"fixed":"3da56dc063cd77b9c0b40add930767fab4e389f3"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-52980.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.12.0"},{"fixed":"6.12.91"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.33"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.0.10"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-52980.json"}}],"schema_version":"1.7.5"}