{"id":"CVE-2025-40237","state":"PUBLISHED","title":"fs/notify: call exportfs_encode_fid with s_umount","description":"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->s_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->s_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<snip registers, unreliable trace>\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->i_sb->s_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/","publishedAt":"2025-12-04T15:31:27.325Z","updatedAt":"2026-05-23T16:01:45.934Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"a1a541fbfa7e97c1100144db34b57553d7164ce5","status":"affected","lessThan":"950b604384fd75d62e860bec7135b2b62eb4d508","versionType":"git"},{"version":"f0c0ac84de17c37e6e84da65fb920f91dada55ad","status":"affected","lessThan":"bc1c6b803e14ea2b8f7e33b7164013f666ceb656","versionType":"git"},{"version":"3c7c90274ae339e1ad443c9be1c67a20b80b9c76","status":"affected","lessThan":"3f307a9f7a7a2822e38ac451b73e2244e7279496","versionType":"git"},{"version":"c45beebfde34aa71afbc48b2c54cdda623515037","status":"affected","lessThan":"d1894bc542becb0fda61e7e513b09523cab44030","versionType":"git"},{"version":"c45beebfde34aa71afbc48b2c54cdda623515037","status":"affected","lessThan":"a7c4bb43bfdc2b9f06ee9d036028ed13a83df42a","versionType":"git"},{"version":"6.6.72","status":"affected","lessThan":"6.6.73","versionType":"semver"},{"version":"6.6.74","status":"affected","lessThan":"6.6.115","versionType":"semver"},{"version":"6.12.10","status":"affected","lessThan":"6.12.56","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/notify/fdinfo.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.13","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.13","versionType":"semver"},{"version":"6.6.73","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.6.115","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.56","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.17.6","status":"unaffected","lessThanOrEqual":"6.17.*","versionType":"semver"},{"version":"6.18","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/notify/fdinfo.c"]}],"references":["https://git.kernel.org/stable/c/950b604384fd75d62e860bec7135b2b62eb4d508","https://git.kernel.org/stable/c/bc1c6b803e14ea2b8f7e33b7164013f666ceb656","https://git.kernel.org/stable/c/3f307a9f7a7a2822e38ac451b73e2244e7279496","https://git.kernel.org/stable/c/d1894bc542becb0fda61e7e513b09523cab44030","https://git.kernel.org/stable/c/a7c4bb43bfdc2b9f06ee9d036028ed13a83df42a"],"weaknesses":[],"ingestedAt":"2026-10-29T20:09:09.358Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2025/40xxx/CVE-2025-40237.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-40237","state":"PUBLISHED","datePublished":"2025-12-04T15:31:27.325Z","dateUpdated":"2026-05-23T16:01:45.934Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2025-04-16T07:20:57.181Z"},"containers":{"cna":{"title":"fs/notify: call exportfs_encode_fid with s_umount","descriptions":[{"lang":"en","value":"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->s_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->s_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<snip registers, unreliable trace>\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->i_sb->s_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/"}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"a1a541fbfa7e97c1100144db34b57553d7164ce5","status":"affected","lessThan":"950b604384fd75d62e860bec7135b2b62eb4d508","versionType":"git"},{"version":"f0c0ac84de17c37e6e84da65fb920f91dada55ad","status":"affected","lessThan":"bc1c6b803e14ea2b8f7e33b7164013f666ceb656","versionType":"git"},{"version":"3c7c90274ae339e1ad443c9be1c67a20b80b9c76","status":"affected","lessThan":"3f307a9f7a7a2822e38ac451b73e2244e7279496","versionType":"git"},{"version":"c45beebfde34aa71afbc48b2c54cdda623515037","status":"affected","lessThan":"d1894bc542becb0fda61e7e513b09523cab44030","versionType":"git"},{"version":"c45beebfde34aa71afbc48b2c54cdda623515037","status":"affected","lessThan":"a7c4bb43bfdc2b9f06ee9d036028ed13a83df42a","versionType":"git"},{"version":"6.6.72","status":"affected","lessThan":"6.6.73","versionType":"semver"},{"version":"6.6.74","status":"affected","lessThan":"6.6.115","versionType":"semver"},{"version":"6.12.10","status":"affected","lessThan":"6.12.56","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/notify/fdinfo.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.13","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.13","versionType":"semver"},{"version":"6.6.73","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.6.115","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.56","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.17.6","status":"unaffected","lessThanOrEqual":"6.17.*","versionType":"semver"},{"version":"6.18","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/notify/fdinfo.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/950b604384fd75d62e860bec7135b2b62eb4d508"},{"url":"https://git.kernel.org/stable/c/bc1c6b803e14ea2b8f7e33b7164013f666ceb656"},{"url":"https://git.kernel.org/stable/c/3f307a9f7a7a2822e38ac451b73e2244e7279496"},{"url":"https://git.kernel.org/stable/c/d1894bc542becb0fda61e7e513b09523cab44030"},{"url":"https://git.kernel.org/stable/c/a7c4bb43bfdc2b9f06ee9d036028ed13a83df42a"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-05-23T16:01:45.934Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6.72","versionEndExcluding":"6.6.73"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6.74","versionEndExcluding":"6.6.115"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12.10","versionEndExcluding":"6.12.56"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.13","versionEndExcluding":"6.17.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.13","versionEndExcluding":"6.18"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}