Commit a189d035 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Linus Torvalds
Browse files

kprobes: disable preempt for module_text_address() and kernel_text_address() 



__register_kprobe() can be preempted after checking probing address but
before module_text_address() or try_module_get(), and in this interval
the module can be unloaded.  In that case, try_module_get(probed_mod)
will access to invalid address, or kprobe will probe invalid address.

This patch uses preempt_disable() to protect it and uses
__module_text_address() and __kernel_text_address().

Signed-off-by: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: default avatarMasami Hiramatsu <mhiramat@redhat.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3b1b3f6e

kernel/kprobes.c

+16 −5
Original line number Diff line number Diff line
@@ -613,30 +613,37 @@ static int __kprobes __register_kprobe(struct kprobe *p, 
		return -EINVAL;

	p->addr = addr;



	if (!kernel_text_address((unsigned long) p->addr) ||

	    in_kprobes_functions((unsigned long) p->addr))

	preempt_disable();

	if (!__kernel_text_address((unsigned long) p->addr) ||

	    in_kprobes_functions((unsigned long) p->addr)) {

		preempt_enable();

		return -EINVAL;

	}



	p->mod_refcounted = 0;



	/*

	 * Check if are we probing a module.

	 */

	probed_mod = module_text_address((unsigned long) p->addr);

	probed_mod = __module_text_address((unsigned long) p->addr);

	if (probed_mod) {

		struct module *calling_mod = module_text_address(called_from);

		struct module *calling_mod;

		calling_mod = __module_text_address(called_from);

		/*

		 * We must allow modules to probe themself and in this case

		 * avoid incrementing the module refcount, so as to allow

		 * unloading of self probing modules.

		 */

		if (calling_mod && calling_mod != probed_mod) {

			if (unlikely(!try_module_get(probed_mod)))

			if (unlikely(!try_module_get(probed_mod))) {

				preempt_enable();

				return -EINVAL;

			}

			p->mod_refcounted = 1;

		} else

			probed_mod = NULL;

	}

	preempt_enable();



	p->nmissed = 0;

	INIT_LIST_HEAD(&p->list);
@@ -718,6 +725,10 @@ static void __kprobes __unregister_kprobe_bottom(struct kprobe *p) 
	struct kprobe *old_p;



	if (p->mod_refcounted) {

		/*

		 * Since we've already incremented refcount,

		 * we don't need to disable preemption.

		 */

		mod = module_text_address((unsigned long)p->addr);

		if (mod)

			module_put(mod);

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