{"id":"CVE-2026-97938","summary":"reboot: fix cad_pid use-after-free race","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nreboot: fix cad_pid use-after-free race\n\ncad_pid is a single kernel-wide struct pid pointer. proc_do_cad_pid()\nreads it and passes it to pid_vnr() without protecting the lifetime of\nthe referenced struct pid. A concurrent writer can replace cad_pid and\ndrop the final reference to the old struct pid after the reader has\nloaded the pointer but before pid_vnr() has finished dereferencing it,\ncausing a use-after-free.\n\nkill_cad_pid() has the same lifetime race when it passes cad_pid to\nkill_pid().\n\nAt the time this issue was reported, an unprivileged user could reach the\nsysctl through user and PID namespaces because cad_pid was registered in\npid_table[]. Moving cad_pid back to the global reboot sysctl table\ncorrected that namespace and permission mismatch, but did not fix the\nunderlying lifetime race.\n\nFix this by treating cad_pid as an RCU-protected pointer at both read\nsites and by waiting for a grace period before dropping the old reference\non the write side.\n\ncall_rcu(&old_pid-\u003ercu, ...) cannot be used here because free_pid()\nalso queues pid-\u003ercu; queueing the same rcu_head twice can corrupt the\nRCU callback list.\n\nOriginal KASAN crash stack:\n  kernel/pid.c:545 pid_nr_ns()        # reads freed pid-\u003elevel\n  kernel/pid.c:556 pid_vnr()          # calls pid_nr_ns()\n  kernel/pid.c:775 proc_do_cad_pid()  # calls pid_vnr(cad_pid)","modified":"2026-09-27T03:47:32.004967461Z","published":"2026-09-25T10:22:51.720Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/97xxx/CVE-2026-97938.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/5a88f78df753993469dab4d1831f8fb4256a9468"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9a17b0e053197a6a42cdc75e75a35b17aa662088"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ad72e2566643fff7f01666d845fb026898155e1f"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/97xxx/CVE-2026-97938.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-97938"},{"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":"9ec52099e4b8678a60e9f93e41ad87885d64f3e6"},{"fixed":"ad72e2566643fff7f01666d845fb026898155e1f"},{"fixed":"9a17b0e053197a6a42cdc75e75a35b17aa662088"},{"fixed":"5a88f78df753993469dab4d1831f8fb4256a9468"}]}],"versions":["v7.2.6","v6.18.52","v7.2.5","v6.18.51","v7.2.4","v6.18.50","v7.2.3","v6.18.49","v7.2.2","v6.18.48","v7.2","v7.2.1","v6.18.47","v6.18.46","v6.18.45","v7.2-rc1","v7.2-rc5","v6.18.44","v7.2-rc7","v7.2-rc2","v7.2-rc6","v7.2-rc3","v6.18.43","v6.18.42","v7.2-rc4","v6.18.41","v6.18.40","v6.18.39","v6.18.38","v6.18.37","v6.18.36","v7.1","v7.1-rc1","v6.18.35","v7.1-rc7","v7.1-rc6","v7.1-rc4","v7.1-rc3","v6.18.34","v7.1-rc2","v7.1-rc5","v6.18.33","v6.18.32","v7.0","v6.18.31","v6.18.30","v6.18.29","v6.18.28","v6.18.27","v6.18.26","v7.0-rc1","v6.18.25","v6.18.24","v6.18.23","v6.18.22","v7.0-rc5","v7.0-rc6","v6.18.21","v7.0-rc7","v7.0-rc3","v7.0-rc4","v6.19-rc2","v6.18.20","v7.0-rc2","v6.19","v6.18.19","v6.18.18","v6.18.17","v6.18.16","v6.18.15","v6.18.14","v6.18.13","v6.18.12","v6.18.11","v6.18.10","v6.18.9","v6.19-rc8","v6.19-rc1","v6.19-rc6","v6.18.8","v6.19-rc7","v6.19-rc5","v6.19-rc4","v6.18.7","v6.19-rc3","v6.18.6","v6.18.5","v6.18.4","v6.18.3","v6.18.2","v6.18.1","v6.18","v6.18-rc1","v6.18-rc7","v6.18-rc3","v6.18-rc5","v6.18-rc6","v6.18-rc2","v6.18-rc4","v6.17","v6.17-rc7","v6.17-rc1","v6.17-rc2","v6.17-rc6","v6.17-rc4","v6.17-rc5","v6.17-rc3","v6.16","v6.16-rc6","v6.16-rc1","v6.16-rc4","v6.16-rc2","v6.16-rc5","v6.16-rc7","v6.16-rc3","v6.14-rc3","v6.15","v6.15-rc1","v6.15-rc6","v6.15-rc3","v6.15-rc2","v6.15-rc7","v6.15-rc4","v6.15-rc5","v6.14","v6.14-rc1","v6.14-rc7","v6.14-rc6","v6.14-rc4","v6.14-rc5","v6.14-rc2","v6.13","v6.13-rc1","v6.13-rc6","v6.13-rc7","v6.13-rc2","v6.13-rc5","v6.13-rc3","v6.12-rc1","v6.13-rc4","v6.12","v6.12-rc7","v6.12-rc3","v6.12-rc4","v6.12-rc6","v6.12-rc5","v6.12-rc2","v6.11-rc1","v6.11-rc5","v6.11","v6.11-rc7","v6.10-rc1","v6.11-rc6","v6.11-rc3","v6.11-rc4","v6.11-rc2","v6.10","v6.10-rc6","v6.10-rc7","v6.10-rc3","v6.9-rc1","v6.10-rc5","v6.10-rc2","v6.10-rc4","v6.9","v6.9-rc6","v6.9-rc7","v6.9-rc5","v6.9-rc3","v6.9-rc2","v6.8","v6.9-rc4","v6.8-rc1","v6.7-rc1","v6.8-rc7","v6.8-rc6","v6.8-rc5","v6.8-rc4","v6.8-rc3","v6.8-rc2","v6.7","v6.7-rc3","v6.7-rc8","v6.7-rc7","v6.7-rc6","v6.7-rc2","v6.7-rc4","v6.7-rc5","v6.6","v6.6-rc1","v6.6-rc5","v6.6-rc3","v6.6-rc7","v6.6-rc6","v6.6-rc4","v6.6-rc2","v6.5","v6.5-rc1","v6.5-rc2","v6.5-rc7","v6.5-rc4","v6.5-rc3","v6.5-rc6","v6.5-rc5","v6.4","v6.4-rc7","v6.4-rc1","v6.4-rc6","v6.4-rc5","v6.4-rc3","v6.4-rc4","v6.4-rc2","v6.3","v6.3-rc1","v6.3-rc7","v6.3-rc2","v6.3-rc3","v6.3-rc5","v6.3-rc6","v6.3-rc4","v6.2-rc6","v6.2-rc1","v6.2","v6.2-rc2","v6.2-rc8","v6.2-rc5","v6.2-rc4","v6.2-rc7","v6.2-rc3","v6.1-rc1","v6.1","v6.1-rc8","v6.1-rc3","v6.1-rc6","v6.1-rc7","v6.1-rc4","v6.1-rc2","v6.1-rc5","v6.0-rc1","v6.0","v6.0-rc7","v6.0-rc3","v6.0-rc2","v6.0-rc6","v6.0-rc4","v6.0-rc5","v5.19","v5.19-rc1","v5.19-rc5","v5.19-rc8","v5.19-rc6","v5.18","v5.19-rc2","v5.19-rc7","v5.19-rc3","v5.19-rc4","v5.18-rc1","v5.18-rc7","v5.18-rc2","v5.18-rc5","v5.17","v5.18-rc4","v5.18-rc3","v5.18-rc6","v5.17-rc6","v5.17-rc4","v5.17-rc8","v5.17-rc7","v5.17-rc1","v5.17-rc3","v5.17-rc2","v5.17-rc5","v5.16","v5.16-rc1","v5.16-rc8","v5.16-rc5","v5.16-rc6","v5.16-rc7","v5.16-rc3","v5.16-rc2","v5.16-rc4","v5.15","v5.15-rc2","v5.15-rc1","v5.15-rc4","v5.15-rc7","v5.15-rc3","v5.15-rc5","v5.15-rc6","v5.14","v5.14-rc3","v5.14-rc1","v5.14-rc2","v5.14-rc7","v5.14-rc6","v5.13-rc1","v5.14-rc5","v5.14-rc4","v5.13","v5.13-rc6","v5.13-rc7","v5.13-rc3","v5.13-rc2","v5.13-rc4","v5.13-rc5","v5.12","v5.12-rc2","v5.12-rc1-dontuse","v5.12-rc1","v5.12-rc8","v5.12-rc3","v5.12-rc7","v5.12-rc5","v5.12-rc6","v5.12-rc4","v5.10","v5.11","v5.11-rc3","v5.11-rc7","v5.11-rc6","v5.11-rc5","v5.11-rc1","v5.11-rc4","v5.11-rc2","v5.10-rc1","v5.10-rc7","v5.10-rc4","v5.10-rc3","v5.10-rc6","v5.9","v5.10-rc2","v5.10-rc5","v5.9-rc1","v5.9-rc7","v5.9-rc8","v5.9-rc6","v5.9-rc4","v5.9-rc5","v5.9-rc3","v5.9-rc2","v5.8","v5.7","v5.8-rc2","v5.8-rc1","v5.8-rc7","v5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