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CVE-2025-40237fs/notify: call exportfs_encode_fid with s_umount

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/

Timeline

  1. ID reserved

    By Linux

  2. · 8 months later

    Published

  3. · 6 months later

    Record updated

Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.

Scores

No CVSS score yet: neither the CNA, CISA nor NVD has scored this CVE. NVD status: Deferred.

EPSS (exploitation in 30 days)
0.22% · top 88% of all CVEs (13 Nov 2026)
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The list uses the assigner's score when there is one, then CISA's, then NVD's: Not scored.

Affected products

  • Linux · Linux

    • affected a1a541fbfa7e97c1100144db34b57553d7164ce5 – < 950b604384fd75d62e860bec7135b2b62eb4d508
    • affected f0c0ac84de17c37e6e84da65fb920f91dada55ad – < bc1c6b803e14ea2b8f7e33b7164013f666ceb656
    • affected 3c7c90274ae339e1ad443c9be1c67a20b80b9c76 – < 3f307a9f7a7a2822e38ac451b73e2244e7279496
    • affected c45beebfde34aa71afbc48b2c54cdda623515037 – < d1894bc542becb0fda61e7e513b09523cab44030
    • affected c45beebfde34aa71afbc48b2c54cdda623515037 – < a7c4bb43bfdc2b9f06ee9d036028ed13a83df42a
    • affected 6.6.72 – < 6.6.73
    • affected 6.6.74 – < 6.6.115
    • affected 6.12.10 – < 6.12.56

  • Linux · Linux

    • affected 6.13
    • unaffected < 6.13
    • unaffected 6.6.73 – ≤ 6.6.*
    • unaffected 6.6.115 – ≤ 6.6.*
    • unaffected 6.12.56 – ≤ 6.12.*
    • unaffected 6.17.6 – ≤ 6.17.*
    • unaffected 6.18 – ≤ *

References

References5

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated .