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[POWERPC] Harden validate_sp against stack corruption 

If something has overflowed or corrupted the stack and causes an oops,
and we try to print a stack trace, that will call validate_sp, which
can itself cause an oops if the cpu field of the thread_info struct at
the bottom of the stack has been corrupted (if CONFIG_IRQSTACKS is
set).  This makes debugging harder.

To avoid the second oops, this adds a check to make sure that the cpu
number is reasonable before using it to check whether the stack is on
the softirq or hardirq stack.

Signed-off-by: Paul Mackerras <paulus@samba.org>
This commit is contained in:
Paul Mackerras 2007-02-19 11:42:42 +11:00
parent 99ddef9bfe
commit bb72c481e9
1 changed files with 30 additions and 13 deletions
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43
arch/powerpc/kernel/process.c
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@ -818,6 +818,35 @@ int sys_execve(unsigned long a0, unsigned long a1, unsigned long a2,
return error;
}
#ifdef CONFIG_IRQSTACKS
static inline int valid_irq_stack(unsigned long sp, struct task_struct *p,
unsigned long nbytes)
{
unsigned long stack_page;
unsigned long cpu = task_cpu(p);
/*
* Avoid crashing if the stack has overflowed and corrupted
* task_cpu(p), which is in the thread_info struct.
*/
if (cpu < NR_CPUS && cpu_possible(cpu)) {
stack_page = (unsigned long) hardirq_ctx[cpu];
if (sp >= stack_page + sizeof(struct thread_struct)
&& sp <= stack_page + THREAD_SIZE - nbytes)
return 1;
stack_page = (unsigned long) softirq_ctx[cpu];
if (sp >= stack_page + sizeof(struct thread_struct)
&& sp <= stack_page + THREAD_SIZE - nbytes)
return 1;
}
return 0;
}
#else
#define valid_irq_stack(sp, p, nb) 0
#endif /* CONFIG_IRQSTACKS */
int validate_sp(unsigned long sp, struct task_struct *p,
unsigned long nbytes)
{
@ -827,19 +856,7 @@ int validate_sp(unsigned long sp, struct task_struct *p,
&& sp <= stack_page + THREAD_SIZE - nbytes)
return 1;
#ifdef CONFIG_IRQSTACKS
stack_page = (unsigned long) hardirq_ctx[task_cpu(p)];
if (sp >= stack_page + sizeof(struct thread_struct)
&& sp <= stack_page + THREAD_SIZE - nbytes)
return 1;
stack_page = (unsigned long) softirq_ctx[task_cpu(p)];
if (sp >= stack_page + sizeof(struct thread_struct)
&& sp <= stack_page + THREAD_SIZE - nbytes)
return 1;
#endif
return 0;
return valid_irq_stack(sp, p, nbytes);
}
#ifdef CONFIG_PPC64