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Message-ID: <2025122409-CVE-2023-54099-4143@gregkh> Date: Wed, 24 Dec 2025 14:06:56 +0100 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-cve-announce@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...nel.org> Subject: CVE-2023-54099: fs: Protect reconfiguration of sb read-write from racing writes From: Greg Kroah-Hartman <gregkh@...nel.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/00000000000006a0df05f6667499@google.com/T/ The Linux kernel CVE team has assigned CVE-2023-54099 to this issue. Affected and fixed versions =========================== Fixed in 5.4.253 with commit 0336b42456e485fda1006b5b411e7372e20fbf03 Fixed in 5.10.190 with commit 7e4e87ec56aa6d008c64eab31b340a7c452b26cc Fixed in 5.15.126 with commit 0ccfe21949bc9f706a86ee7351b74375c0745757 Fixed in 6.1.45 with commit 295ef44a2abaf97d7a594b1d4c60d4be3738191f Fixed in 6.4.10 with commit 4abda85197ba5d695e6040d580b4b409ce0d3733 Fixed in 6.5 with commit c541dce86c537714b6761a79a969c1623dfa222b Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2023-54099 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: fs/super.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/0336b42456e485fda1006b5b411e7372e20fbf03 https://git.kernel.org/stable/c/7e4e87ec56aa6d008c64eab31b340a7c452b26cc https://git.kernel.org/stable/c/0ccfe21949bc9f706a86ee7351b74375c0745757 https://git.kernel.org/stable/c/295ef44a2abaf97d7a594b1d4c60d4be3738191f https://git.kernel.org/stable/c/4abda85197ba5d695e6040d580b4b409ce0d3733 https://git.kernel.org/stable/c/c541dce86c537714b6761a79a969c1623dfa222b
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