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The vulnerability CVE-2025-38306 is a race condition flaw within the `fs/fhandle.c` file of the Linux kernel. The issue occurs in the `may_decode_fh()` function, which insecurely calls `has_locked_children()` without holding any necessary locks. This creates a time-of-check-to-time-of-use (TOCTOU) race window where the state of a mount point can change after `has_locked_children()` checks it but before `may_decode_fh()` acts on that information. Specifically, the function checks if a mount has locked children, but because it operates without the protection of `mount_lock` or namespace_sem, the mount structure could be concurrently modified or freed. This lack of synchronization can lead to the kernel accessing invalid memory, resulting in a crash (kernel oops) or other undefined behavior, potentially allowing for denial-of-service.
Platform: Linux Kernel
Version: Up to fix
Vulnerability : Race Condition
Severity: High
date: 07/10/2025
Prediction: Patch expected by 07/24/2025
What Undercode Say:
grep -r "has_locked_children" /usr/src/linux-kernel-source/ cat /proc/mounts | head -20
// In fs/fhandle.c
int may_decode_fh(...) {
// ... missing lock ...
if (has_locked_children(mnt, ...)) // RACE CONDITION HERE
}
How Exploit:
Endless loop triggering `may_decode_fh` via `open_by_handle_at` concurrently with unmount operations. Causes kernel panic.
Protection from this CVE
Apply kernel patch. Update system. Avoid untrusted filesystems.
Impact:
Kernel crash. Denial-of-service. System instability.
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Sources:
Reported By: nvd.nist.gov
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