On Sat, Jul 2, 2016 at 11:34 AM, Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote:
> On Sat, Jul 02, 2016 at 07:24:41PM +0200, Borislav Petkov wrote:
>> On Sun, Jun 26, 2016 at 02:55:32PM -0700, Andy Lutomirski wrote:
>> > It's not going to work, because the scheduler will explode if we try
>> > to schedule when running on an IST stack or similar.
>> >
>> > This will matter when we let kernel stack overflows (which are #DF)
>> > call die().
>> >
>> > Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
>> > ---
>> > arch/x86/kernel/dumpstack.c | 3 +++
>> > 1 file changed, 3 insertions(+)
>> >
>> > diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
>> > index ef8017ca5ba9..352f022cfd5b 100644
>> > --- a/arch/x86/kernel/dumpstack.c
>> > +++ b/arch/x86/kernel/dumpstack.c
>> > @@ -245,6 +245,9 @@ void oops_end(unsigned long flags, struct pt_regs *regs, int signr)
>> > return;
>> > if (in_interrupt())
>> > panic("Fatal exception in interrupt");
>> > + if (((current_stack_pointer() ^ (current_top_of_stack() - 1))
>> > + & ~(THREAD_SIZE - 1)) != 0)
>>
>> Ugh, that's hard to parse. You could remove the "!= 0" at least to
>> shorten it a bit and have one less braces level.
>>
>> Or maybe even do something like that to make it a bit more readable:
>>
>> if ((current_stack_pointer() ^ (current_top_of_stack() - 1))
>> &
>> ~(THREAD_SIZE - 1))
>> panic("Fatal exception on non-default stack");
>>
>> Meh.
>
> A helper function would be even better.
>
> The existing 'object_is_on_stack()' can probably be used:
>
> if (!object_is_on_stack(current_top_of_stack()))
> panic("...");
>
> Though that function isn't quite accurately named. It should really
> have 'task_stack' in its name, like 'object_is_on_task_stack()'. Or
> even better, something more concise like 'on_task_stack()'.
>
Given that the very next patch deletes this code, I vote for leaving
it alone. Or I could fold the patches together.
--Andy
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