Use After Free Affecting kernel-rt-debug-kvm package, versions *

Note: Versions mentioned in the description apply only to the upstream kernel-rt-debug-kvm package and not the kernel-rt-debug-kvm package as distributed by Centos. See How to fix? for Centos:7 relevant fixed versions and status.

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

bus: mhi: core: Fix invalid error returning in mhi_queue

mhi_queue returns an error when the doorbell is not accessible in the current state. This can happen when the device is in non M0 state, like M3, and needs to be waken-up prior ringing the DB. This case is managed earlier by triggering an asynchronous M3 exit via controller resume/suspend callbacks, that in turn will cause M0 transition and DB update.

So, since it's not an error but just delaying of doorbell update, there is no reason to return an error.

This also fixes a use after free error for skb case, indeed a caller queuing skb will try to free the skb if the queueing fails, but in that case queueing has been done.

• https://access.redhat.com/security/cve/CVE-2021-46969
• https://git.kernel.org/stable/c/0ecc1c70dcd32c0f081b173a1a5d89952686f271
• https://git.kernel.org/stable/c/a99b661c3187365f81026d89b1133a76cd2652b3