linux-kernel - Re: CVE-2024-38630: watchdog: cpu5wdt.c: Fix use-after-free bug caused by cpu5wdt

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Message-ID: <20241011172723.46827821@endymion.delvare>
Date: Fri, 11 Oct 2024 17:27:23 +0200
From: Jean Delvare <jdelvare@...e.de>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: cve@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: CVE-2024-38630: watchdog: cpu5wdt.c: Fix use-after-free bug
 caused by cpu5wdt_trigger

Hi Greg,

On Fri, 11 Oct 2024 15:34:18 +0200, Greg Kroah-Hartman wrote:
> On Fri, Oct 11, 2024 at 12:16:40PM +0200, Jean Delvare wrote:
> > On Fri, 2024-06-21 at 12:19 +0200, Greg Kroah-Hartman wrote:  
> > > Description
> > > ===========
> > > 
> > > In the Linux kernel, the following vulnerability has been resolved:
> > > 
> > > watchdog: cpu5wdt.c: Fix use-after-free bug caused by cpu5wdt_trigger
> > > 
> > > When the cpu5wdt module is removing, the origin code uses del_timer() to
> > > de-activate the timer. If the timer handler is running, del_timer() could
> > > not stop it and will return directly. If the port region is released by
> > > release_region() and then the timer handler cpu5wdt_trigger() calls outb()
> > > to write into the region that is released, the use-after-free bug will
> > > happen.
> > > 
> > > Change del_timer() to timer_shutdown_sync() in order that the timer handler
> > > could be finished before the port region is released.
> > > 
> > > The Linux kernel CVE team has assigned CVE-2024-38630 to this issue.
> > > 
> > > 
> > > Affected and fixed versions
> > > ===========================
> > > 
> > >         Issue introduced in 3.8 with commit e09d9c3e9f85 and fixed in 6.6.33 with commit 9b1c063ffc07
> > >         Issue introduced in 3.8 with commit e09d9c3e9f85 and fixed in 6.9.4 with commit f19686d61650
> > >         Issue introduced in 3.8 with commit e09d9c3e9f85 and fixed in 6.10-rc1 with commit 573601521277  
> > 
> > For the record, this is incorrect. The Fixes tag is misleading. The
> > commit being "fixed" was adding a missing del_timer() call, so the
> > situation was even worst before that, as the race window on module
> > removal was even larger.
> > 
> > The bug is present since kernel v2.5.61 when the cpu5wdt driver was
> > added to the kernel tree.  
> 
> So should I change the "vulnerable" commit to be the root of git, commit
> 1da177e4c3f4 ("Linux-2.6.12-rc2"), instead?

Yes.

-- 
Jean Delvare
SUSE L3 Support