[PATCH] Harden validate_sp against stack corruption
From: Paul Mackerras <hidden>
Date: 2007-02-19 00:42:42
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Linus Torvalds
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 <redacted> ---
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index f3d4dd5..3712fd5 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c@@ -818,6 +818,35 @@ out: 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_IRQS && 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