{"id":"CVE-2026-90400","summary":"md: recheck spare changes before starting sync","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nmd: recheck spare changes before starting sync\n\nremove_spares() and remove_and_add_spares() modify the array's rdev\nconfiguration. These operations are only safe after the array has been\nsuspended.\n\nmd_start_sync() checks whether spare configuration changes are needed\nbefore taking reconfig_mutex. However, the rdev state can change before\nthe mutex is acquired, so the initial check can become stale. In that\ncase, md_choose_sync_action() may remove or replace rdevs while normal\nI/O is still accessing them.\n\nThe race can occur as follows:\n\nraid10d          Worker                      Normal IO\n____________     _______________________     ______________________\n\n                                             raid10_write_request()\n                                             wait_blocked_dev()\nset Blocked\nset Faulty\n                                             Skip Faulty rdev\n                                             rrdev-\u003enr_pending++\n                                             .repl_bio = bio\n                 removeable_rdev = false     .\n                 array not suspended         .\nlock mddev                                   goto err_handle\n                 lock mddev (wait)\n                 .\nupdate sb        .\nclear Blocked    .\n                 .\nunlock mddev     .\n                 lock mddev (acquires)\n                 remove_spares()\n                 removeable_rdev = true\n\n                 raid10_remove_disk()\n                 rdev = replacement\n                 replacement = NULL\n                                             rdev_dec_pending(NULL)\n                 unlock mddev                (NULL)-\u003enr_pending--\n\nIn this case, rdev_dec_pending() is called with a NULL pointer,\nresulting in a NULL pointer dereference when attempting to decrement\nnr_pending.\n\nFix this by suspending the array when spare configuration changes are\nneeded, including for non-read-write arrays, and checking again after\ntaking reconfig_mutex. If the array was not already suspended and a\nchange is now needed, release the mutex, suspend the array, and\nreacquire the mutex before continuing.","modified":"2026-09-19T03:47:26.087881705Z","published":"2026-09-17T16:09:30.915Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90400.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/81b39df5d701976cf20e52f33106c1fc1603b4cb"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c3777d16bc3335c0ac4bdad0551c80d38c5d94cc"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c7d34d17ea43ebc86b45d439ebb435e11ca44bca"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e5ac7ab78467b064f1da8b0f3042a63595fafcfd"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90400.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-90400"},{"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":"bc08041b32abe6c9824f78735bac22018eabfc06"},{"fixed":"c3777d16bc3335c0ac4bdad0551c80d38c5d94cc"},{"fixed":"e5ac7ab78467b064f1da8b0f3042a63595fafcfd"},{"fixed":"81b39df5d701976cf20e52f33106c1fc1603b4cb"},{"fixed":"c7d34d17ea43ebc86b45d439ebb435e11ca44bca"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90400.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.110"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.52"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.6"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90400.json"}}],"schema_version":"1.9.0"}