fs/notify: call exportfs_encode_fid with s_umount
Summary
| CVE | CVE-2025-40237 |
|---|---|
| State | PUBLISHED |
| Assigner | Linux |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2025-12-04 16:16:16 UTC |
| Updated | 2026-10-19 21:10:00 UTC |
| Description | In the Linux kernel, the following vulnerability has been resolved: fs/notify: call exportfs_encode_fid with s_umount Calling intotify_show_fdinfo() on fd watching an overlayfs inode, while the overlayfs is being unmounted, can lead to dereferencing NULL ptr. This issue was found by syzkaller. Race Condition Diagram: Thread 1 Thread 2 -------- -------- generic_shutdown_super() shrink_dcache_for_umount sb->s_root = NULL | | vfs_read() | inotify_fdinfo() | * inode get from mark * | show_mark_fhandle(m, inode) | exportfs_encode_fid(inode, ..) | ovl_encode_fh(inode, ..) | ovl_check_encode_origin(inode) | * deref i_sb->s_root * | | v fsnotify_sb_delete(sb) Which then leads to: [ 32.133461] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000006: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI [ 32.134438] KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037] [ 32.135032] CPU: 1 UID: 0 PID: 4468 Comm: systemd-coredum Not tainted 6.17.0-rc6 #22 PREEMPT(none) <snip registers, unreliable trace> [ 32.143353] Call Trace: [ 32.143732] ovl_encode_fh+0xd5/0x170 [ 32.144031] exportfs_encode_inode_fh+0x12f/0x300 [ 32.144425] show_mark_fhandle+0xbe/0x1f0 [ 32.145805] inotify_fdinfo+0x226/0x2d0 [ 32.146442] inotify_show_fdinfo+0x1c5/0x350 [ 32.147168] seq_show+0x530/0x6f0 [ 32.147449] seq_read_iter+0x503/0x12a0 [ 32.148419] seq_read+0x31f/0x410 [ 32.150714] vfs_read+0x1f0/0x9e0 [ 32.152297] ksys_read+0x125/0x240 IOW ovl_check_encode_origin derefs inode->i_sb->s_root, after it was set to NULL in the unmount path. Fix it by protecting calling exportfs_encode_fid() from show_mark_fhandle() with s_umount lock. This form of fix was suggested by Amir in [1]. [1]: https://lore.kernel.org/all/CAOQ4uxhbDwhb+2Brs1UdkoF0a3NSdBAOQPNfEHjahrgoKJpLEw@mail.gmail.com/ |
Risk And Classification
EPSS: 0.002010000 probability, percentile 0.094100000 (date 2026-10-19)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Linux | Linux | affected a1a541fbfa7e97c1100144db34b57553d7164ce5 950b604384fd75d62e860bec7135b2b62eb4d508 git | Not specified |
| CNA | Linux | Linux | affected f0c0ac84de17c37e6e84da65fb920f91dada55ad bc1c6b803e14ea2b8f7e33b7164013f666ceb656 git | Not specified |
| CNA | Linux | Linux | affected 3c7c90274ae339e1ad443c9be1c67a20b80b9c76 3f307a9f7a7a2822e38ac451b73e2244e7279496 git | Not specified |
| CNA | Linux | Linux | affected c45beebfde34aa71afbc48b2c54cdda623515037 d1894bc542becb0fda61e7e513b09523cab44030 git | Not specified |
| CNA | Linux | Linux | affected c45beebfde34aa71afbc48b2c54cdda623515037 a7c4bb43bfdc2b9f06ee9d036028ed13a83df42a git | Not specified |
| CNA | Linux | Linux | affected 6.6.72 6.6.73 semver | Not specified |
| CNA | Linux | Linux | affected 6.6.74 6.6.115 semver | Not specified |
| CNA | Linux | Linux | affected 6.12.10 6.12.56 semver | Not specified |
| CNA | Linux | Linux | affected 6.13 | Not specified |
| CNA | Linux | Linux | unaffected 6.13 semver | Not specified |
| CNA | Linux | Linux | unaffected 6.6.73 6.6.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.6.115 6.6.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.12.56 6.12.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.17.6 6.17.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.18 * original_commit_for_fix | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| git.kernel.org/stable/c/950b604384fd75d62e860bec7135b2b62eb4d508 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/3f307a9f7a7a2822e38ac451b73e2244e7279496 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/d1894bc542becb0fda61e7e513b09523cab44030 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/a7c4bb43bfdc2b9f06ee9d036028ed13a83df42a | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/bc1c6b803e14ea2b8f7e33b7164013f666ceb656 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
There are currently no legacy QID mappings associated with this CVE.