Use After Free Affecting kernel-rt-debug-modules-extra package, versions <0:4.18.0-553.8.1.rt7.349.el8_10

Note: Versions mentioned in the description apply only to the upstream kernel-rt-debug-modules-extra package and not the kernel-rt-debug-modules-extra 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:

mISDN: fix possible use-after-free in HFC_cleanup()

This module's remove path calls del_timer(). However, that function does not wait until the timer handler finishes. This means that the timer handler may still be running after the driver's remove function has finished, which would result in a use-after-free.

Fix by calling del_timer_sync(), which makes sure the timer handler has finished, and unable to re-schedule itself.

• https://access.redhat.com/security/cve/CVE-2021-47356
• https://git.kernel.org/stable/c/009fc857c5f6fda81f2f7dd851b2d54193a8e733
• https://git.kernel.org/stable/c/3ecd228c636ee17c14662729737fa07242a93cb0
• https://git.kernel.org/stable/c/49331c07ef0f8fdfa42b30ba6a83a657b29d7fbe
• https://git.kernel.org/stable/c/54ff3202928952a100c477248e65ac6db01258a7
• https://git.kernel.org/stable/c/5f2818185da0fe82a932f0856633038b66faf124
• https://git.kernel.org/stable/c/61370ff07e0acc657559a8fac02551dfeb9d3020
• https://git.kernel.org/stable/c/7867ddc5f3de7f289aee63233afc0df4b62834c5
• https://git.kernel.org/stable/c/b7ee9ae1e0cf55a037c4a99af2acc5d78cb7802d
• https://git.kernel.org/stable/c/ed7c3739d0a07e2ec3ccbffe7e93cea01c438cda