Improper Locking Affecting kernel-rt-core package, versions *

Note: Versions mentioned in the description apply only to the upstream kernel-rt-core package and not the kernel-rt-core package as distributed by Centos. See How to fix? for Centos:8 relevant fixed versions and status.

In the Linux kernel, the following vulnerability has been resolved:

net: ks8851: Queue RX packets in IRQ handler instead of disabling BHs

Currently the driver uses local_bh_disable()/local_bh_enable() in its IRQ handler to avoid triggering net_rx_action() softirq on exit from netif_rx(). The net_rx_action() could trigger this driver .start_xmit callback, which is protected by the same lock as the IRQ handler, so calling the .start_xmit from netif_rx() from the IRQ handler critical section protected by the lock could lead to an attempt to claim the already claimed lock, and a hang.

The local_bh_disable()/local_bh_enable() approach works only in case the IRQ handler is protected by a spinlock, but does not work if the IRQ handler is protected by mutex, i.e. this works for KS8851 with Parallel bus interface, but not for KS8851 with SPI bus interface.

Remove the BH manipulation and instead of calling netif_rx() inside the IRQ handler code protected by the lock, queue all the received SKBs in the IRQ handler into a queue first, and once the IRQ handler exits the critical section protected by the lock, dequeue all the queued SKBs and push them all into netif_rx(). At this point, it is safe to trigger the net_rx_action() softirq, since the netif_rx() call is outside of the lock that protects the IRQ handler.

• https://access.redhat.com/security/cve/CVE-2024-36962
• https://git.kernel.org/stable/c/7e2901a2a9195da76111f351584bf77552a038f0
• https://git.kernel.org/stable/c/8a3ff43dcbab7c96f9e8cf2bd1049ab8d6e59545
• https://git.kernel.org/stable/c/ae87f661f3c1a3134a7ed86ab69bf9f12af88993
• https://git.kernel.org/stable/c/e0863634bf9f7cf36291ebb5bfa2d16632f79c49