Re: [CHECKER] large stack variables (>=1K) in 2.4.4 and 2.4.4-ac8

Brian Gerst
2001-05-25T12:07:56Z

Andi Kleen wrote:
>
> On Fri, May 25, 2001 at 07:52:02AM -0400, Brian Gerst wrote:
> > Actually, you will never get a stack fault exception, since with a flat
> > stack segment you can never get a limit violation. All you will do is
> > corrupt the data in task struct and cause an oops later on when the
> > kernel tries to use the task struct. There are only two ways to
> > properly trap a kernel stack overflow:
>
> In my experience the stack pointer eventually gets corrupted and starts
> pointing to some unmapped area, which gives you a stack fault (admittedly
> a backtrace is a bit hard after that)

You mean a double fault. #SS is only called when there is a limit
violation on the stack segment or the stack segment is not present. I
guess you could get a limit violation if it tried to wrap around below
0, but you would get a page fault first. An unmapped page will always
cause a page fault, but since the stack is still invalid, it would then
cause a double fault.

--

Brian Gerst