CVE-2023-54099: In the Linux kernel, the following vulnerability has been resolved: fs: Protect reconfiguration of sb read-write from racing writes The reconfigure / remount

In the Linux kernel, the following vulnerability has been resolved: fs: Protect reconfiguration of sb read-write from racing writes The reconfigure / remount

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/00000000000006a0df05f6667499@google.com/T/

Description from the National Vulnerability Database, published by 416baaa9-dc9f-4396-8d5f-8c081fb06d67

What it means for a small business

Linux is on the computers, phones or browsers your team uses every day. Turn on automatic updates and restart: most of these fixes only take effect after a restart.

How likely is an attack? The Exploit Prediction Scoring System, run by FIRST (the global association of security response teams), puts the odds of this one being exploited in the next 30 days at 0.21%, higher than 11% of CVEs. That’s low, but low isn’t zero, and the odds jump the day someone publishes an exploit. Scored October 29, 2026, updated daily.

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Sources

Part of the Huttenlocher Technologies vulnerability database, refreshed twice a day from CISA and the NVD. The title, category and plain-language guidance are ours; check the linked record before acting on a detail. This is general guidance, not a review of your systems.

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