{"id":"CVE-2026-68150","summary":"fs/super: fix emergency thaw double-unlock of s_umount","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nfs/super: fix emergency thaw double-unlock of s_umount\n\ndo_thaw_all() iterates over all superblocks via __iterate_supers()\nwith SUPER_ITER_EXCL, which acquires s_umount exclusively before\ncalling the callback and releases it afterwards. However, the\ncallback do_thaw_all_callback() calls thaw_super_locked() which\nunconditionally releases s_umount on every code path. This results\nin a second unlock attempt in __iterate_supers() that corrupts the\nrwsem state, triggering a DEBUG_RWSEMS warning:\n\n[  182.601148] sysrq: Emergency Thaw of all frozen filesystems\n[  182.601865] ------------[ cut here ]------------\n[  182.602375] DEBUG_RWSEMS_WARN_ON((rwsem_owner(sem) != current) && !rwsem_test_oflags(sem, RWSEM_NONSPINNABLE)): count = 0x0, magic = 0xffff99b1011e5870, owner = 0x0, curr 0xffff99b101b06c80, list not empty\n[  182.603817] WARNING: kernel/locking/rwsem.c:1412 at up_write+0xa3/0x170, CPU#2: kworker/2:1/53\n[  182.604578] Modules linked in:\n[  182.604864] CPU: 2 UID: 0 PID: 53 Comm: kworker/2:1 Not tainted 7.2.0-rc4-00001-gbd3bd93ea98a-dirty #4 PREEMPT(lazy)\n[  182.605711] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1kylin1 04/01/2014\n[  182.606417] Workqueue: events do_thaw_all\n[  182.606750] RIP: 0010:up_write+0xaf/0x170\n[  182.607076] Code: 19 3a 92 48 0f 44 c2 48 8b 55 08 48 8b 55 00 4c 8b 45 08 48 8b 55 00 48 8d 3d ad 91 e0 01 48 8b 4d 20 50 48 c7 c6 f0 8c 26 92 \u003c67\u003e 48 0f b9 3a e8 d7 93 4e 00 58 eb 81 48 83 7f 18 00 48 c7 c2 8d\n[  182.608563] RSP: 0018:ffffb670001d7e08 EFLAGS: 00010246\n[  182.609007] RAX: ffffffff92349e8d RBX: 0000000000000000 RCX: ffff99b1011e5870\n[  182.609595] RDX: 0000000000000000 RSI: ffffffff92268cf0 RDI: ffffffff92914d10\n[  182.610283] RBP: ffff99b1011e5870 R08: 0000000000000000 R09: ffff99b101b06c80\n[  182.610847] R10: ffff99b10139a808 R11: fefefefefefefeff R12: 0000000000000000\n[  182.611414] R13: ffffffff90cf74d0 R14: 0000000000000000 R15: ffff99b1011e5800\n[  182.612009] FS:  0000000000000000(0000) GS:ffff99b1eaaee000(0000) knlGS:0000000000000000\n[  182.612670] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n[  182.613146] CR2: 00000000005c631c CR3: 00000000013ee000 CR4: 00000000000006f0\n[  182.613722] Call Trace:\n[  182.613946]  \u003cTASK\u003e\n[  182.614130]  __iterate_supers+0x128/0x150\n[  182.614463]  do_thaw_all+0x1b/0x30\n[  182.614759]  process_scheduled_works+0xbb/0x3f0\n[  182.615150]  ? __pfx_worker_thread+0x10/0x10\n[  182.615499]  worker_thread+0x129/0x270\n[  182.615816]  ? __pfx_worker_thread+0x10/0x10\n[  182.616201]  kthread+0xe2/0x120\n[  182.616469]  ? __pfx_kthread+0x10/0x10\n[  182.616792]  ret_from_fork+0x15b/0x240\n[  182.617115]  ? __pfx_kthread+0x10/0x10\n[  182.617426]  ret_from_fork_asm+0x1a/0x30\n[  182.617761]  \u003c/TASK\u003e\n[  182.617968] ---[ end trace 0000000000000000 ]---\n[  182.618412] Emergency Thaw complete\n\nFix this by switching to SUPER_ITER_UNLOCKED and acquiring s_umount\nin the callback via super_lock_excl() before calling\nthaw_super_locked(). This matches the locking pattern expected by\nthaw_super_locked() and eliminates the double unlock.\n\nWhile at it, remove the dead 'return;' at the end of\ndo_thaw_all_callback().","modified":"2026-08-25T03:30:39.644636092Z","published":"2026-08-10T11:59:15.647Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/68xxx/CVE-2026-68150.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/503d67fbaec6fdeaba391cb497675071db9d16ea"},{"type":"WEB","url":"https://git.kernel.org/stable/c/64017df6e61a3ce7159cee284109b92009985361"},{"type":"WEB","url":"https://git.kernel.org/stable/c/79e04370657a2581e3189f9c7fc166e7c4fbab3a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c78e38745ff1b0457c4551e7f75ea15842df1169"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/68xxx/CVE-2026-68150.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-68150"},{"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":"96a7883817a29fcbb46f70f0302ed455f7203c74"},{"fixed":"79e04370657a2581e3189f9c7fc166e7c4fbab3a"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"2992476528aeecbaee17ba0a6396a817481205a3"},{"fixed":"c78e38745ff1b0457c4551e7f75ea15842df1169"},{"fixed":"64017df6e61a3ce7159cee284109b92009985361"},{"fixed":"503d67fbaec6fdeaba391cb497675071db9d16ea"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-68150.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.16.0"},{"fixed":"6.18.42"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.1.6"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-68150.json"}}],"schema_version":"1.9.0"}