{"id":"CVE-2026-97971","summary":"nstree: check listing permission before taking a namespace reference","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nnstree: check listing permission before taking a namespace reference\n\nlegitimize_ns() takes a reference on the candidate namespace before\nmay_list_ns() has decided whether the caller may see it. The\n__free(ns_put) cleanup on the denied path can drop the last reference to a\nmount namespace while we still hold the rcu read lock, and put_mnt_ns()\nmay sleep there. This is the same problem commit 2ec2aff3c8e2 (\"ns: make\nsure reference are dropped outside of rcu lock\") fixed for the put_user()\npath. Neither ns_requested() nor may_list_ns() needs a reference, both\nonly look at the namespace type and at the caller's own namespaces, so do\nthe checks first and take the reference last.\n\nSplat:\n\n  Voluntary context switch within RCU read-side critical section!\n  WARNING: kernel/rcu/tree_plugin.h:332 at rcu_note_context_switch+0x238/0x2a0, CPU#5: a/3442\n  CPU: 5 UID: 1000 PID: 3442 Comm: a Not tainted 7.0.0-30-generic #30-Ubuntu PREEMPT(lazy)\n  RIP: 0010:rcu_note_context_switch+0x238/0x2a0\n  Call Trace:\n   \u003cTASK\u003e\n   __schedule+0xcf/0x650\n   schedule+0x27/0x90\n   schedule_preempt_disabled+0x15/0x30\n   __mutex_lock.constprop.0+0x550/0xaf0\n   __mutex_lock_slowpath+0x13/0x20\n   mutex_lock+0x3b/0x50\n   exp_funnel_lock+0xb2/0x260\n   synchronize_rcu_expedited+0xe7/0x220\n   namespace_unlock+0x26a/0x320\n   put_mnt_ns+0xd3/0x120\n   mntns_put+0xe/0x20\n   do_listns+0x13e/0x560\n   __do_sys_listns+0x126/0x2d0\n   __x64_sys_listns+0x20/0x30\n   x64_sys_call+0x2366/0x2390\n   do_syscall_64+0x105/0x5a0\n   entry_SYSCALL_64_after_hwframe+0x76/0x7e\n   \u003c/TASK\u003e","modified":"2026-09-26T03:48:36.797252774Z","published":"2026-09-25T10:23:11.539Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/97xxx/CVE-2026-97971.json"},"references":[{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"},{"type":"WEB","url":"https://git.kernel.org/stable/c/56ea4e86832d8abe8930394473566c194d189f85"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9e673bf5d88aa898e52cef5c87058c3fa845bc71"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/97xxx/CVE-2026-97971.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-97971"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"76b6f5dfb3fda76fce1f9990d6fa58adc711122b"},{"fixed":"9e673bf5d88aa898e52cef5c87058c3fa845bc71"},{"fixed":"56ea4e86832d8abe8930394473566c194d189f85"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-97971.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.7"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-97971.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}