linux-kernel - Re: CVE-2023-52596: sysctl: Fix out of bounds access for empty sysctl registers

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Date: Tue, 12 Mar 2024 10:45:28 +0100
From: Michal Hocko <mhocko@...e.com>
To: Lee Jones <lee@...nel.org>
Cc: Luis Chamberlain <mcgrof@...nel.org>, cve@...nel.org,
	linux-kernel@...r.kernel.org,
	Joel Granados <j.granados@...sung.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: CVE-2023-52596: sysctl: Fix out of bounds access for empty
 sysctl registers

On Tue 12-03-24 09:17:30, Lee Jones wrote:
[...]
> > Backporting this is fine, but wouldn't fix an issue unless an external
> > module had empty sysctls. And exploiting this is not possible unless
> > you purposely build an external module which could end up with empty
> > sysctls.

Thanks for the clarification Luis!

> Thanks for the amazing explanation Luis.
> 
> If I'm reading this correctly, an issue does exist, but an attacker
> would have to lay some foundations before it could be triggered.  Sounds
> like loading of a malicious or naive module would be enough.

If the bar is set as high as a kernel module to create and empty sysctl
directory then I think it is safe to say that the security aspect is
mostly moot. There are much simpler ways to attack the system if you are
able to load a kernel module.

> We know from conducting postmortems on previous exploits that successful
> attacks often consist of leveraging a chain of smaller, seemingly
> implausible or innocuous looking bugs rather than in isolation.
> 
> With that in mind, it is still my belief that this could be used by an
> attacker in such a chain.  Unless I have this totally wrong or any of
> the maintainers have strong feelings to the contrary, I would like to
> keep the CVE number associated with this fix.

No, no real strong feelings but I have to say that I find a CVE more
than a stretch. Kernel modules could do much more harm than just abuse
this particular bug.
-- 
Michal Hocko
SUSE Labs