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[PATCH] s390: show_task oops

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The show_task function walks the kernel stack backchain of processes assuming
that the processes are not running.  Since this assumption is not correct
walking the backchain can lead to an addressing exception and therefore to a
kernel hang.  So prevent the kernel hang (you still get incorrect results)
verity that all read accesses are within the bounds of the kernel stack before
performing them.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Heiko Carstens 2006-01-14 13:20:57 -08:00 committed by Linus Torvalds
parent 7ffbc9da13
commit eb33c190c2
1 changed files with 11 additions and 3 deletions
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14
arch/s390/kernel/process.c
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@ -58,10 +58,18 @@ asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
*/
unsigned long thread_saved_pc(struct task_struct *tsk)
{
struct stack_frame *sf;
struct stack_frame *sf, *low, *high;
sf = (struct stack_frame *) tsk->thread.ksp;
sf = (struct stack_frame *) sf->back_chain;
if (!tsk || !task_stack_page(tsk))
return 0;
low = task_stack_page(tsk);
high = (struct stack_frame *) task_pt_regs(tsk);
sf = (struct stack_frame *) (tsk->thread.ksp & PSW_ADDR_INSN);
if (sf <= low || sf > high)
return 0;
sf = (struct stack_frame *) (sf->back_chain & PSW_ADDR_INSN);
if (sf <= low || sf > high)
return 0;
return sf->gprs[8];
}