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NULL Pointer Dereference The advisory has been revoked - it doesn't affect any version of package kernel-debug-modules-partner  (opens in a new tab)

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EPSS
0.17% (7th percentile)

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  • Snyk IDSNYK-CENTOS9-KERNELDEBUGMODULESPARTNER-7817416
  • published23 Aug 2024
  • disclosed22 Aug 2024
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Introduced: 22 Aug 2024

CVE-2022-48921  (opens in a new tab)
CWE-476  (opens in a new tab)

Amendment

The Centos security team deemed this advisory irrelevant for Centos:9.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-debug-modules-partner package and not the kernel-debug-modules-partner package as distributed by Centos.

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

sched/fair: Fix fault in reweight_entity

Syzbot found a GPF in reweight_entity. This has been bisected to commit 4ef0c5c6b5ba ("kernel/sched: Fix sched_fork() access an invalid sched_task_group")

There is a race between sched_post_fork() and setpriority(PRIO_PGRP) within a thread group that causes a null-ptr-deref in reweight_entity() in CFS. The scenario is that the main process spawns number of new threads, which then call setpriority(PRIO_PGRP, 0, -20), wait, and exit. For each of the new threads the copy_process() gets invoked, which adds the new task_struct and calls sched_post_fork() for it.

In the above scenario there is a possibility that setpriority(PRIO_PGRP) and set_one_prio() will be called for a thread in the group that is just being created by copy_process(), and for which the sched_post_fork() has not been executed yet. This will trigger a null pointer dereference in reweight_entity(), as it will try to access the run queue pointer, which hasn't been set.

Before the mentioned change the cfs_rq pointer for the task has been set in sched_fork(), which is called much earlier in copy_process(), before the new task is added to the thread_group. Now it is done in the sched_post_fork(), which is called after that. To fix the issue the remove the update_load param from the update_load param() function and call reweight_task() only if the task flag doesn't have the TASK_NEW flag set.