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

[Brian Gerst <bgerst@didntduck.org>]

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