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

[Michal Hocko]

On Wed 06-03-24 06:45:54, Greg KH wrote:
> Description
> ===========
> 
> In the Linux kernel, the following vulnerability has been resolved:
> 
> sysctl: Fix out of bounds access for empty sysctl registers
> 
> When registering tables to the sysctl subsystem there is a check to see
> if header is a permanently empty directory (used for mounts). This check
> evaluates the first element of the ctl_table. This results in an out of
> bounds evaluation when registering empty directories.
> 
> The function register_sysctl_mount_point now passes a ctl_table of size
> 1 instead of size 0. It now relies solely on the type to identify
> a permanently empty register.
> 
> Make sure that the ctl_table has at least one element before testing for
> permanent emptiness.

While this makes the code more robust and more future proof I do not think
this is fixing any real issue not to mention anything with security
implications. AFAIU there is no actual code that can generate empty
sysctl directories unless the kernel is heavily misconfigured.

Luis, Joel, what do you think?

-- 
Michal Hocko
SUSE Labs