From eb33c190c2b633f0dfc98481ecf12f62a02c705e Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Sat, 14 Jan 2006 13:20:57 -0800 Subject: [PATCH] [PATCH] s390: show_task oops 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 Signed-off-by: Martin Schwidefsky Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/s390/kernel/process.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c index 2ff90a1a105..008c74526fd 100644 --- a/arch/s390/kernel/process.c +++ b/arch/s390/kernel/process.c @@ -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]; } -- 2.20.1