Re: [PATCH v2] Restrict unprivileged access to kernel syslog

[Ingo Molnar]

* Dan Rosenberg <drosenberg@xxxxxxxxxxxxx> wrote:

> The kernel syslog contains debugging information that is often useful
> during exploitation of other vulnerabilities, such as kernel heap
> addresses.  Rather than futilely attempt to sanitize hundreds (or
> thousands) of printk statements and simultaneously cripple useful
> debugging functionality, it is far simpler to create an option that
> prevents unprivileged users from reading the syslog.
> 
> This patch, loosely based on grsecurity's GRKERNSEC_DMESG, creates the
> dmesg_restrict sysctl.  When set to "0", the default, no restrictions
> are enforced.  When set to "1", only users with CAP_SYS_ADMIN can read
> the kernel syslog via dmesg(8) or other mechanisms.
> 
> v2 adds CONFIG_SECURITY_RESTRICT_DMESG.  When enabled, the default
> sysctl value is set to "1".  When disabled, the default sysctl value is
> set to "0".
> 
> Signed-off-by: Dan Rosenberg <drosenberg@xxxxxxxxxxxxx>
> CC: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> CC: Ingo Molnar <mingo@xxxxxxx>
> CC: Kees Cook <kees.cook@xxxxxxxxxxxxx>
> CC: stable <stable@xxxxxxxxxx>

Acked-by: Ingo Molnar <mingo@xxxxxxx>

Linus, Andrew, any objections against pushing this trivial control flag upstream out 
of band, after a bit of testing? It's not like it can break anything, and the flag 
is very useful to distros.

Thanks,

	Ingo
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