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[AVR32] show_trace: Only walk valid stack addresses

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Terminate the frame pointer walk if (a) the address is outside the
task's kernel stack or (b) if the frame pointer isn't monotonically
increasing. Without this fix, show_trace() may enter an infinite
loop, walking through random data anywhere in memory.

Since any address within the kernel stack is guaranteed to be valid,
we may eliminate the __get_user() calls as well.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
This commit is contained in:
Haavard Skinnemoen 2007-02-21 13:08:06 +01:00
parent 9a596a6236
commit 3338368e92
1 changed files with 28 additions and 22 deletions
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50
arch/avr32/kernel/traps.c
View File

@ -49,39 +49,45 @@ out:
return;
}
static inline int valid_stack_ptr(struct thread_info *tinfo, unsigned long p)
{
return (p > (unsigned long)tinfo)
&& (p < (unsigned long)tinfo + THREAD_SIZE - 3);
}
#ifdef CONFIG_FRAME_POINTER
static inline void __show_trace(struct task_struct *tsk, unsigned long *sp,
struct pt_regs *regs)
{
unsigned long __user *fp;
unsigned long __user *last_fp = NULL;
unsigned long lr, fp;
struct thread_info *tinfo;
if (regs) {
fp = (unsigned long __user *)regs->r7;
} else if (tsk == current) {
register unsigned long __user *real_fp __asm__("r7");
fp = real_fp;
} else {
fp = (unsigned long __user *)tsk->thread.cpu_context.r7;
}
tinfo = (struct thread_info *)
((unsigned long)sp & ~(THREAD_SIZE - 1));
if (regs)
fp = regs->r7;
else if (tsk == current)
asm("mov %0, r7" : "=r"(fp));
else
fp = tsk->thread.cpu_context.r7;
/*
* Walk the stack until (a) we get an exception, (b) the frame
* pointer becomes zero, or (c) the frame pointer gets stuck
* at the same value.
* Walk the stack as long as the frame pointer (a) is within
* the kernel stack of the task, and (b) it doesn't move
* downwards.
*/
while (fp && fp != last_fp) {
unsigned long lr, new_fp = 0;
last_fp = fp;
if (__get_user(lr, fp))
break;
if (fp && __get_user(new_fp, fp + 1))
break;
fp = (unsigned long __user *)new_fp;
while (valid_stack_ptr(tinfo, fp)) {
unsigned long new_fp;
lr = *(unsigned long *)fp;
printk(" [<%08lx>] ", lr);
print_symbol("%s\n", lr);
new_fp = *(unsigned long *)(fp + 4);
if (new_fp <= fp)
break;
fp = new_fp;
}
printk("\n");
}