title: sh: push-switch: Reorder cleanup operations to avoid use-after-free bug
description: In the Linux kernel, the following vulnerability has been resolved:
sh: push-switch: Reorder cleanup operations to avoid use-after-free bug
The original code puts flush_work() before timer_shutdown_sync()
in switch_drv_remove(). Although we use flush_work() to stop
the worker, it could be rescheduled in switch_timer(). As a result,
a use-after-free bug can occur. The details are shown below:
(cpu 0)                    |      (cpu 1)
switch_drv_remove()              |
flush_work()                    |
...                            |  switch_timer // timer
|   schedule_work(&psw->work)
timer_shutdown_sync()           |
...                             |  switch_work_handler // worker
kfree(psw) // free              |
|   psw->state = 0 // use
This patch puts timer_shutdown_sync() before flush_work() to
mitigate the bugs. As a result, the worker and timer will be
stopped safely before the deallocate operations.
affected:
{
product: Linux
vendor: Linux
defaultStatus: unaffected
repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
versions:
version: 9f5e8eee5cfe, lessThan: 610dbd8ac271, status: affected, versionType: git
version: 9f5e8eee5cfe, lessThan: 246f80a0b17f, status: affected, versionType: git
}
{
product: Linux
vendor: Linux
defaultStatus: affected
repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
versions:
version: 2.6.20, status: affected
version: 0, lessThan: 2.6.20, status: unaffected, versionType: custom
version: 6.5.4, lessThanOrEqual: 6.5.*, status: unaffected, versionType: custom
version: 6.6, lessThanOrEqual: *, status: unaffected, versionType: original_commit_for_fix
}
