{"id":"CVE-2026-93182","state":"PUBLISHED","title":"sched/fair: Fix overflow in update_tg_cfs_runnable()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nsched/fair: Fix overflow in update_tg_cfs_runnable()\n\nA divide-by-zero crash is observed when running hackbench:\n\n   [14697.488452] CPU: 112 UID: 0 PID: 124791 Comm: hackbench Not tainted 7.1.0-rc2+\n   [14697.492627] RIP: 0010:propagate_entity_load_avg+0x35f/0x3e0\n   [14697.506799]  <TASK>\n   [14697.507411]  __dequeue_task+0x2b4/0xc70\n   [14697.508677]  dequeue_task_fair+0x36/0x370\n   [14697.509047]  dequeue_task+0x101/0x2f0\n   [14697.509426]  __schedule+0x1b1/0x1a00\n   [14697.510868]  anon_pipe_read+0x3da/0x450\n   [14697.511400]  vfs_read+0x361/0x390\n   [14697.512053]  __x64_sys_read+0x19/0x30\n\nThe divide-by-zero happens here:\n\n  if (scale_load_down(gcfs_rq->load.weight)) {\n           load_sum = div_u64(gcfs_rq->avg.load_sum,\n                              scale_load_down(gcfs_rq->load.weight));\n  }\n\ngcfs_rq->load.weight is an insane large value and is truncated\nto the lower 32 bits by div_u64, which happen to be 0.\n\nUsing AI for investigation, the cause is a u32 overflow in\nupdate_tg_cfs_runnable(), and flat pickup became a victim when using\ntg_tasks():\n\n   u32 new_sum, divider;\n   ...\n   new_sum = se->avg.runnable_avg * divider; <-- boom\n\nThe following sequence shows how this triggers the crash:\n\n   propagate_entity_load_avg()\n     update_tg_cfs_runnable()     # u32 overflow corrupts runnable_sum\n\n   __update_load_avg_cfs_rq()\n     ___update_load_avg()         # computes insane runnable_avg\n   update_tg_load_avg()           # propagates to tg->runnable_avg\n\n   update_cfs_group()\n     calc_concur_shares()\n       tg_tasks()                 # long-to-int truncation, negative nr\n     reweight_entity()            # corrupted se->load.weight\n       update_load_add()          # corrupted cfs_rq->load.weight\n\n   propagate_entity_load_avg()\n     update_tg_cfs_load()\n       div_u64()                  # divide-by-zero\n\nFix by widening new_sum from u32 to u64 (no need to force tg_tasks()\nto return unsigned long after this fix)","publishedAt":"2026-09-17T16:12:09.381Z","updatedAt":"2026-10-19T09:06:55.184Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"95246d1ec80b8d19d882cd8eb7ad094e63b41bb8","status":"affected","lessThan":"39d707097a0820c6e87eff4195f0940e8ff1147e","versionType":"git"},{"version":"95246d1ec80b8d19d882cd8eb7ad094e63b41bb8","status":"affected","lessThan":"69fafae4eb2c9fc9bcff1bcbfcccf5d197434d75","versionType":"git"},{"version":"95246d1ec80b8d19d882cd8eb7ad094e63b41bb8","status":"affected","lessThan":"7cc237e3bc1733928313d2462b413ae441b0eef3","versionType":"git"},{"version":"95246d1ec80b8d19d882cd8eb7ad094e63b41bb8","status":"affected","lessThan":"18fdd0978ec3dda0ff6865cd273e47e022180710","versionType":"git"},{"version":"95246d1ec80b8d19d882cd8eb7ad094e63b41bb8","status":"affected","lessThan":"f94e62d21faad5e244d0874598a4d0ebbc0ea405","versionType":"git"},{"version":"95246d1ec80b8d19d882cd8eb7ad094e63b41bb8","status":"affected","lessThan":"4f166adb5cb0525d9e32d45729fd8f28c80acbee","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/sched/fair.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.17","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.17","versionType":"semver"},{"version":"6.1.188","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.157","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.110","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.52","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.6","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/sched/fair.c"]}],"references":["https://git.kernel.org/stable/c/39d707097a0820c6e87eff4195f0940e8ff1147e","https://git.kernel.org/stable/c/69fafae4eb2c9fc9bcff1bcbfcccf5d197434d75","https://git.kernel.org/stable/c/7cc237e3bc1733928313d2462b413ae441b0eef3","https://git.kernel.org/stable/c/18fdd0978ec3dda0ff6865cd273e47e022180710","https://git.kernel.org/stable/c/f94e62d21faad5e244d0874598a4d0ebbc0ea405","https://git.kernel.org/stable/c/4f166adb5cb0525d9e32d45729fd8f28c80acbee"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:34.582Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/93xxx/CVE-2026-93182.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-93182","state":"PUBLISHED","datePublished":"2026-09-17T16:12:09.381Z","dateUpdated":"2026-10-19T09:06:55.184Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-17T16:02:15.091Z"},"containers":{"cna":{"title":"sched/fair: Fix overflow in update_tg_cfs_runnable()","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nsched/fair: Fix overflow in update_tg_cfs_runnable()\n\nA divide-by-zero crash is observed when running hackbench:\n\n   [14697.488452] CPU: 112 UID: 0 PID: 124791 Comm: hackbench Not tainted 7.1.0-rc2+\n   [14697.492627] RIP: 0010:propagate_entity_load_avg+0x35f/0x3e0\n   [14697.506799]  <TASK>\n   [14697.507411]  __dequeue_task+0x2b4/0xc70\n   [14697.508677]  dequeue_task_fair+0x36/0x370\n   [14697.509047]  dequeue_task+0x101/0x2f0\n   [14697.509426]  __schedule+0x1b1/0x1a00\n   [14697.510868]  anon_pipe_read+0x3da/0x450\n   [14697.511400]  vfs_read+0x361/0x390\n   [14697.512053]  __x64_sys_read+0x19/0x30\n\nThe divide-by-zero happens here:\n\n  if (scale_load_down(gcfs_rq->load.weight)) {\n           load_sum = div_u64(gcfs_rq->avg.load_sum,\n                              scale_load_down(gcfs_rq->load.weight));\n  }\n\ngcfs_rq->load.weight is an insane large value and is truncated\nto the lower 32 bits by div_u64, which happen to be 0.\n\nUsing AI for investigation, the cause is a u32 overflow in\nupdate_tg_cfs_runnable(), and flat pickup became a victim when using\ntg_tasks():\n\n   u32 new_sum, divider;\n   ...\n   new_sum = se->avg.runnable_avg * divider; <-- boom\n\nThe following sequence shows how this triggers the crash:\n\n   propagate_entity_load_avg()\n     update_tg_cfs_runnable()     # u32 overflow corrupts runnable_sum\n\n   __update_load_avg_cfs_rq()\n     ___update_load_avg()         # computes insane runnable_avg\n   update_tg_load_avg()           # propagates to tg->runnable_avg\n\n   update_cfs_group()\n     calc_concur_shares()\n       tg_tasks()                 # long-to-int truncation, negative nr\n     reweight_entity()            # corrupted se->load.weight\n       update_load_add()          # corrupted cfs_rq->load.weight\n\n   propagate_entity_load_avg()\n     update_tg_cfs_load()\n       div_u64()                  # divide-by-zero\n\nFix by widening new_sum from u32 to u64 (no need to force tg_tasks()\nto return unsigned long after this fix)"}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"95246d1ec80b8d19d882cd8eb7ad094e63b41bb8","status":"affected","lessThan":"39d707097a0820c6e87eff4195f0940e8ff1147e","versionType":"git"},{"version":"95246d1ec80b8d19d882cd8eb7ad094e63b41bb8","status":"affected","lessThan":"69fafae4eb2c9fc9bcff1bcbfcccf5d197434d75","versionType":"git"},{"version":"95246d1ec80b8d19d882cd8eb7ad094e63b41bb8","status":"affected","lessThan":"7cc237e3bc1733928313d2462b413ae441b0eef3","versionType":"git"},{"version":"95246d1ec80b8d19d882cd8eb7ad094e63b41bb8","status":"affected","lessThan":"18fdd0978ec3dda0ff6865cd273e47e022180710","versionType":"git"},{"version":"95246d1ec80b8d19d882cd8eb7ad094e63b41bb8","status":"affected","lessThan":"f94e62d21faad5e244d0874598a4d0ebbc0ea405","versionType":"git"},{"version":"95246d1ec80b8d19d882cd8eb7ad094e63b41bb8","status":"affected","lessThan":"4f166adb5cb0525d9e32d45729fd8f28c80acbee","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/sched/fair.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.17","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.17","versionType":"semver"},{"version":"6.1.188","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.157","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.110","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.52","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.6","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/sched/fair.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/39d707097a0820c6e87eff4195f0940e8ff1147e"},{"url":"https://git.kernel.org/stable/c/69fafae4eb2c9fc9bcff1bcbfcccf5d197434d75"},{"url":"https://git.kernel.org/stable/c/7cc237e3bc1733928313d2462b413ae441b0eef3"},{"url":"https://git.kernel.org/stable/c/18fdd0978ec3dda0ff6865cd273e47e022180710"},{"url":"https://git.kernel.org/stable/c/f94e62d21faad5e244d0874598a4d0ebbc0ea405"},{"url":"https://git.kernel.org/stable/c/4f166adb5cb0525d9e32d45729fd8f28c80acbee"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T09:06:55.184Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17","versionEndExcluding":"6.1.188"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17","versionEndExcluding":"6.6.157"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17","versionEndExcluding":"6.12.110"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17","versionEndExcluding":"6.18.52"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17","versionEndExcluding":"7.2.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.17","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}