{"id":"CVE-2025-40237","summary":"fs/notify: call exportfs_encode_fid with s_umount","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nfs/notify: call exportfs_encode_fid with s_umount\n\nCalling intotify_show_fdinfo() on fd watching an overlayfs inode, while\nthe overlayfs is being unmounted, can lead to dereferencing NULL ptr.\n\nThis issue was found by syzkaller.\n\nRace Condition Diagram:\n\nThread 1                           Thread 2\n--------                           --------\n\ngeneric_shutdown_super()\n shrink_dcache_for_umount\n  sb-\u003es_root = NULL\n\n                    |\n                    |             vfs_read()\n                    |              inotify_fdinfo()\n                    |               * inode get from mark *\n                    |               show_mark_fhandle(m, inode)\n                    |                exportfs_encode_fid(inode, ..)\n                    |                 ovl_encode_fh(inode, ..)\n                    |                  ovl_check_encode_origin(inode)\n                    |                   * deref i_sb-\u003es_root *\n                    |\n                    |\n                    v\n fsnotify_sb_delete(sb)\n\nWhich then leads to:\n\n[   32.133461] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000006: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI\n[   32.134438] KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037]\n[   32.135032] CPU: 1 UID: 0 PID: 4468 Comm: systemd-coredum Not tainted 6.17.0-rc6 #22 PREEMPT(none)\n\n\u003csnip registers, unreliable trace\u003e\n\n[   32.143353] Call Trace:\n[   32.143732]  ovl_encode_fh+0xd5/0x170\n[   32.144031]  exportfs_encode_inode_fh+0x12f/0x300\n[   32.144425]  show_mark_fhandle+0xbe/0x1f0\n[   32.145805]  inotify_fdinfo+0x226/0x2d0\n[   32.146442]  inotify_show_fdinfo+0x1c5/0x350\n[   32.147168]  seq_show+0x530/0x6f0\n[   32.147449]  seq_read_iter+0x503/0x12a0\n[   32.148419]  seq_read+0x31f/0x410\n[   32.150714]  vfs_read+0x1f0/0x9e0\n[   32.152297]  ksys_read+0x125/0x240\n\nIOW ovl_check_encode_origin derefs inode-\u003ei_sb-\u003es_root, after it was set\nto NULL in the unmount path.\n\nFix it by protecting calling exportfs_encode_fid() from\nshow_mark_fhandle() with s_umount lock.\n\nThis form of fix was suggested by Amir in [1].\n\n[1]: https://lore.kernel.org/all/CAOQ4uxhbDwhb+2Brs1UdkoF0a3NSdBAOQPNfEHjahrgoKJpLEw@mail.gmail.com/","modified":"2026-05-18T05:57:29.667814236Z","published":"2025-12-04T15:31:27.325Z","related":["SUSE-SU-2026:20207-1","SUSE-SU-2026:20220-1","SUSE-SU-2026:20228-1","openSUSE-SU-2026:20145-1"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/40xxx/CVE-2025-40237.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/3f307a9f7a7a2822e38ac451b73e2244e7279496"},{"type":"WEB","url":"https://git.kernel.org/stable/c/950b604384fd75d62e860bec7135b2b62eb4d508"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a7c4bb43bfdc2b9f06ee9d036028ed13a83df42a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/bc1c6b803e14ea2b8f7e33b7164013f666ceb656"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d1894bc542becb0fda61e7e513b09523cab44030"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/40xxx/CVE-2025-40237.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-40237"},{"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":"a1a541fbfa7e97c1100144db34b57553d7164ce5"},{"fixed":"950b604384fd75d62e860bec7135b2b62eb4d508"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"f0c0ac84de17c37e6e84da65fb920f91dada55ad"},{"fixed":"bc1c6b803e14ea2b8f7e33b7164013f666ceb656"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"3c7c90274ae339e1ad443c9be1c67a20b80b9c76"},{"fixed":"3f307a9f7a7a2822e38ac451b73e2244e7279496"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"c45beebfde34aa71afbc48b2c54cdda623515037"},{"fixed":"d1894bc542becb0fda61e7e513b09523cab44030"},{"fixed":"a7c4bb43bfdc2b9f06ee9d036028ed13a83df42a"}]}],"versions":["v6.6.72","v6.6.114","v6.6.113","v6.6.112","v6.6.111","v6.6.110","v6.6.109","v6.6.108","v6.6.107","v6.6.106","v6.6.105","v6.6.104","v6.6.103","v6.6.102","v6.6.101","v6.6.100","v6.6.99","v6.6.98","v6.6.97","v6.6.96","v6.6.95","v6.6.94","v6.6.93","v6.6.92","v6.6.91","v6.6.90","v6.6.89","v6.6.88","v6.6.87","v6.6.86","v6.6.85","v6.6.84","v6.6.83","v6.6.82","v6.6.81","v6.6.80","v6.6.79","v6.6.78","v6.6.77","v6.6.76","v6.6.75","v6.6.74","v6.12.55","v6.12.54","v6.12.53","v6.12.52","v6.12.51","v6.12.50","v6.12.49","v6.12.48","v6.12.47","v6.12.46","v6.12.45","v6.12.44","v6.12.43","v6.12.42","v6.12.41","v6.12.40","v6.12.39","v6.12.38","v6.12.37","v6.12.36","v6.12.35","v6.12.34","v6.12.33","v6.12.32","v6.12.31","v6.12.30","v6.12.29","v6.12.28","v6.12.27","v6.12.26","v6.12.25","v6.12.24","v6.12.23","v6.12.22","v6.12.21","v6.12.20","v6.12.19","v6.12.18","v6.12.17","v6.12.16","v6.12.15","v6.12.14","v6.12.13","v6.12.12","v6.12.11","v6.12.10"],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2025-40237.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.6.73"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.6.115"},{"fixed":"6.12.56"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.17.6"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2025-40237.json"}}],"schema_version":"1.7.5"}