Linux Kernel SCX_KICK_WAIT Deadlock Vulnerability in Scheduler Extension

A deadlock vulnerability has been identified in the Linux kernel's scheduler extension, specifically within the SCX_KICK_WAIT mechanism. This issue arises when the SCX_KICK_WAIT feature busy-waits in the 'kick_cpus_irq_workfn' function, using 'smp_cond_load_acquire' until the target CPU's 'kick_sync' status advances. Since 'irq_work' operates in a hard interrupt context, the waiting CPU cannot reschedule, causing its own 'kick_sync' to stagnate. This situation can lead to a deadlock if multiple CPUs form a waiting cycle. The vulnerability is present in Linux kernel versions 6.12 and later.

Impact

Exploitation of this vulnerability can lead to a deadlock situation where multiple CPUs are stuck waiting for each other, causing a halt in processing and potentially leading to a system freeze.

Remediation

Users can upgrade to the latest version of the Linux kernel to address this vulnerability. The fixed version is included in the official Linux kernel stable releases.