Re: [PATCH 4/4] arm64/syscalls: Move address limit check in loop

[Kees Cook <keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>]

On Tue, Sep 12, 2017 at 11:27 AM, Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org> wrote:
> Hi Kees,
>
> On Thu, Sep 07, 2017 at 08:30:47AM -0700, Kees Cook wrote:
>> From: Thomas Garnier <thgarnie-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
>>
>> A bug was reported on ARM where set_fs might be called after it was
>> checked on the work pending function. ARM64 is not affected by this bug
>> but has a similar construct. In order to avoid any similar problems in
>> the future, the addr_limit_user_check function is moved at the beginning
>> of the loop.
>>
>> Fixes: cf7de27ab351 ("arm64/syscalls: Check address limit on user-mode return")
>> Reported-by: Leonard Crestez <leonard.crestez-3arQi8VN3Tc@public.gmane.org>
>> Signed-off-by: Thomas Garnier <thgarnie-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
>> Signed-off-by: Kees Cook <keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
>> ---
>>  arch/arm64/kernel/signal.c | 6 +++---
>>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> What's the plan for this series? It looks like somehow an old v2 of the
> original series made it into mainline, so I'd like to see these fixes get
> in ASAP. I'm still slightly nervous about pathological setting of the
> FSCHECK flag due to e.g. a PMU IRQ causing a livelock in do_notify_resume,
> but that's at least less likely with this fix :/

Hi! I resent this to Ingo to pick up for -tip. I think he's waiting
for -rc1, IIUC. Ingo, can you comment on timing for this getting sent
to Linus?

-Kees

-- 
Kees Cook
Pixel Security