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SubjectRe: [RESEND][PATCH] proc: Fix timerslack_ns CAP_SYS_NICE check when adjusting self
On Tue, Aug 30, 2016 at 4:06 PM, Andrew Morton
<akpm@linux-foundation.org> wrote:
> On Tue, 30 Aug 2016 18:46:23 -0400 Kees Cook <keescook@chromium.org> wrote:
>
>> On Mon, Aug 22, 2016 at 7:01 PM, John Stultz <john.stultz@linaro.org> wrote:
>> > In changing from checking ptrace_may_access(p, PTRACE_MODE_ATTACH_FSCREDS)
>> > to capable(CAP_SYS_NICE), I missed that ptrace_my_access succeeds
>> > when p == current, but the CAP_SYS_NICE doesn't.
>> >
>> > Thus while the previous commit was intended to loosen the needed
>> > privledges to modify a processes timerslack, it needlessly restricted
>> > a task modifying its own timerslack via the proc/<tid>/timerslack_ns
>> > (which is permitted also via the PR_SET_TIMERSLACK method).
>> >
>> > This patch corrects this by checking if p == current before checking
>> > the CAP_SYS_NICE value.
>> >
>> > This patch applies on top of my two previous patches currently in -mm
>> >
>> > Cc: Kees Cook <keescook@chromium.org>
>> > Cc: "Serge E. Hallyn" <serge@hallyn.com>
>> > Cc: Andrew Morton <akpm@linux-foundation.org>
>> > Cc: Thomas Gleixner <tglx@linutronix.de>
>> > CC: Arjan van de Ven <arjan@linux.intel.com>
>> > Cc: Oren Laadan <orenl@cellrox.com>
>> > Cc: Ruchi Kandoi <kandoiruchi@google.com>
>> > Cc: Rom Lemarchand <romlem@android.com>
>> > Cc: Todd Kjos <tkjos@google.com>
>> > Cc: Colin Cross <ccross@android.com>
>> > Cc: Nick Kralevich <nnk@google.com>
>> > Cc: Dmitry Shmidt <dimitrysh@google.com>
>> > Cc: Elliott Hughes <enh@google.com>
>> > Cc: Android Kernel Team <kernel-team@android.com>
>> > Acked-by: Kees Cook <keescook@chromium.org>
>> > Signed-off-by: John Stultz <john.stultz@linaro.org>
>>
>> Andrew, can you take this for v4.8?
>
> Well, it fixes
> proc-relax-proc-tid-timerslack_ns-capability-requirements.patch,
> somewhat. And it textually depends on that.
>
> Do we want all of
>
> proc-relax-proc-tid-timerslack_ns-capability-requirements.patch
> proc-add-lsm-hook-checks-to-proc-tid-timerslack_ns.patch
> proc-fix-timerslack_ns-cap_sys_nice-check-when-adjusting-self.patch
>
> in 4.8? If so, why?

No.. they're fine to wait for the 4.9 merge window. But you picking up
this last fix is appreciated!

thanks
-john

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