CVE-2023-54099
Unknown Unknown - Not Provided
Race Condition in Linux Kernel Filesystem Remount Allows Premature Writes

Publication date: 2025-12-24

Last updated on: 2025-12-24

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: fs: Protect reconfiguration of sb read-write from racing writes The reconfigure / remount code takes a lot of effort to protect filesystem's reconfiguration code from racing writes on remounting read-only. However during remounting read-only filesystem to read-write mode userspace writes can start immediately once we clear SB_RDONLY flag. This is inconvenient for example for ext4 because we need to do some writes to the filesystem (such as preparation of quota files) before we can take userspace writes so we are clearing SB_RDONLY flag before we are fully ready to accept userpace writes and syzbot has found a way to exploit this [1]. Also as far as I'm reading the code the filesystem remount code was protected from racing writes in the legacy mount path by the mount's MNT_READONLY flag so this is relatively new problem. It is actually fairly easy to protect remount read-write from racing writes using sb->s_readonly_remount flag so let's just do that instead of having to workaround these races in the filesystem code. [1] https://lore.kernel.org/all/[email protected]/T/
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Meta Information
Published
2025-12-24
Last Modified
2025-12-24
Generated
2026-05-07
AI Q&A
2025-12-24
EPSS Evaluated
2026-05-05
NVD
CVE-2023-54099
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-UNKNOWN
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability involves a race condition in the Linux kernel's filesystem remount code. When remounting a filesystem from read-only to read-write mode, the system clears the SB_RDONLY flag before it is fully ready to accept user writes. This allows userspace writes to start prematurely, which can cause issues such as improper preparation of quota files in ext4. The problem arises because the protection against racing writes that existed in the legacy mount path is missing in the newer code, allowing exploitation of this race condition.


How can this vulnerability impact me? :

This vulnerability can lead to filesystem inconsistencies or corruption because userspace writes may begin before the filesystem is fully prepared to handle them during a remount from read-only to read-write. For example, necessary filesystem preparations like quota file setup may be incomplete, potentially causing data integrity issues.


What immediate steps should I take to mitigate this vulnerability?

The vulnerability has been resolved in the Linux kernel by protecting the remount read-write operation from racing writes using the sb->s_readonly_remount flag. To mitigate this vulnerability, you should update your Linux kernel to the version that includes this fix.


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