Description

In the Linux kernel, the following vulnerability has been resolved:

fsnotify: clear PARENT_WATCHED flags lazily

In some setups directories can have many (usually negative) dentries.
Hence __fsnotify_update_child_dentry_flags() function can take a
significant amount of time. Since the bulk of this function happens
under inode->i_lock this causes a significant contention on the lock
when we remove the watch from the directory as the
__fsnotify_update_child_dentry_flags() call from fsnotify_recalc_mask()
races with __fsnotify_update_child_dentry_flags() calls from
__fsnotify_parent() happening on children. This can lead upto softlockup
reports reported by users.

Fix the problem by calling fsnotify_update_children_dentry_flags() to
set PARENT_WATCHED flags only when parent starts watching children.

When parent stops watching children, clear false positive PARENT_WATCHED
flags lazily in __fsnotify_parent() for each accessed child.

Classification

CVE ID: CVE-2024-47660

CVSS Base Severity: MEDIUM

CVSS Base Score: 4.7

CVSS Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected Products

Vendor: Linux

Product: Linux

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.02% (probability of being exploited)

EPSS Percentile: 4.55% (scored less or equal to compared to others)

EPSS Date: 2025-06-02 (when was this score calculated)

Stakeholder-Specific Vulnerability Categorization (SSVC)

SSVC Exploitation: none

SSVC Technical Impact: partial

SSVC Automatable: false

References

https://nvd.nist.gov/vuln/detail/CVE-2024-47660
https://git.kernel.org/stable/c/3f3ef1d9f66b93913ce2171120d9226b55acd41d
https://git.kernel.org/stable/c/f9a48bc3dd9099935751458a5bbbea4b7c28abc8
https://git.kernel.org/stable/c/d8c42405fc3507cc43ba7e4986a773c3fc633f6e
https://git.kernel.org/stable/c/fc1b1e135c3f72382f792e6c319fc088d5523ad5
https://git.kernel.org/stable/c/7ef1d2e240c32b1f337a37232d037b07e3919e1a
https://git.kernel.org/stable/c/172e422ffea20a89bfdc672741c1aad6fbb5044e

Timeline