{"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":"2026-04-02T12:48:20.254168Z","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":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/40xxx/CVE-2025-40237.json","cna_assigner":"Linux"},"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"}]}],"database_specific":{"source":"https://storage.googleapis.com/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/cve-osv-conversion/osv-output/CVE-2025-40237.json"}}],"schema_version":"1.7.5"}