linux-kernel - Re: CVE-2022-48921: sched/fair: Fix fault in reweight

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Message-ID: <2024082539-balancing-rematch-d61d@gregkh>
Date: Sun, 25 Aug 2024 07:54:40 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Xia Fukun <xiafukun@...wei.com>
Cc: cve@...nel.org, linux-kernel@...r.kernel.org,
	linux-cve-announce@...r.kernel.org,
	"Zhangqiao (2012 lab)" <zhangqiao22@...wei.com>,
	"Chenhui (Judy)" <judy.chenhui@...wei.com>
Subject: Re: CVE-2022-48921: sched/fair: Fix fault in reweight_entity

On Sat, Aug 24, 2024 at 05:52:05PM +0800, Xia Fukun wrote:
> 
> On 2024/8/22 11:31, Greg Kroah-Hartman wrote:
> > Description
> > ===========
> > 
> > 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.
> > 
> > 
> > The Linux kernel CVE team has assigned CVE-2022-48921 to this issue.
> > 
> 
> Commit 13765de8148f ("sched/fair: Fix fault in reweight_entity")
> is reverted by commit b1e8206582f9 ("sched: Fix yet more sched_fork()
> races"). Since commit 13765de8148f only fixes a single instance
> of this problem, not the whole class.
> 
> I think the CVE-2022-48921 needs to adjust the corresponding commit
> to commit b1e8206582f9 ("sched: Fix yet more sched_fork() races").

I think we just need to assign a new CVE to b1e8206582f9, as that was
not backported to everywhere that 13765de8148f was applied, right?
Wouldn't that be the correct thing to do as it did fix things in a
different way.

thanks,

greg k-h