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How the mentioned CVE works:
The vulnerability is in the Linux kernel’s fbnic driver. During power management resume, the driver’s service_task attempts to call phylink_resume to bring the network interface online. This operation requires the RTNL (Real-Time Networking Lock) to be held. However, the driver invokes phylink_resume while enabling the service_task in the fbnic_up path, which occurs without holding RTNL. This triggers a locking assertion failure in the phylink subsystem at line 2611 of phylink.c. The kernel logs a warning and may cause instability or failure during system resume from sleep states, potentially disrupting network functionality. The fix moves the phylink resume call into the ndo_open/close paths where proper locking is enforced.
Platform: Linux kernel
Version: Pre-patch versions
Vulnerability: Locking assertion failure
Severity: Medium
date: 09/16/2025
Prediction: Patch available 09/2025
What Undercode Say:
Trigger PM suspend/resume cycle
echo mem > /sys/power/state
In QEMU monitor for wakeup
system_wakeup
Check kernel logs for warning
dmesg | grep -i “phylink_resume”
Code snippet from kernel log showing assert
[ 42.208116][ T164] RTNL: assertion failed at drivers/net/phy/phylink.c (2611)
[ 42.208492][ T164] WARNING: CPU: 1 PID: 164 at drivers/net/phy/phylink.c:2611 phylink_resume+0x190/0x1e0
how Exploit:
Repeatedly trigger system suspend/resume cycles to cause kernel warnings or potential denial of service due to locking violations.
Protection from this CVE
Apply kernel patch updating fbnic driver to move phylink resume into open/close paths.
Impact:
System instability during resume, network interface failures.
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Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
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