CVE-2021-47356 Information

Description

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.

Reference

https://git.kernel.org/stable/c/49331c07ef0f8fdfa42b30ba6a83a657b29d7fbe https://git.kernel.org/stable/c/54ff3202928952a100c477248e65ac6db01258a7 https://git.kernel.org/stable/c/7867ddc5f3de7f289aee63233afc0df4b62834c5 https://git.kernel.org/stable/c/5f2818185da0fe82a932f0856633038b66faf124 https://git.kernel.org/stable/c/3ecd228c636ee17c14662729737fa07242a93cb0 https://git.kernel.org/stable/c/b7ee9ae1e0cf55a037c4a99af2acc5d78cb7802d https://git.kernel.org/stable/c/61370ff07e0acc657559a8fac02551dfeb9d3020 https://git.kernel.org/stable/c/ed7c3739d0a07e2ec3ccbffe7e93cea01c438cda https://git.kernel.org/stable/c/009fc857c5f6fda81f2f7dd851b2d54193a8e733