Commit 297f9233 authored by Jessica Yu's avatar Jessica Yu Committed by Ingo Molnar
Browse files

kprobes: Propagate error from disarm_kprobe_ftrace() 

Improve error handling when disarming ftrace-based kprobes. Like with
arm_kprobe_ftrace(), propagate any errors from disarm_kprobe_ftrace() so
that we do not disable/unregister kprobes that are still armed. In other
words, unregister_kprobe() and disable_kprobe() should not report success
if the kprobe could not be disarmed.

disarm_all_kprobes() keeps its current behavior and attempts to
disarm all kprobes. It returns the last encountered error and gives a
warning if not all probes could be disarmed.

This patch is based on Petr Mladek's original patchset (patches 2 and 3)
back in 2015, which improved kprobes error handling, found here:

   https://lkml.org/lkml/2015/2/26/452



However, further work on this had been paused since then and the patches
were not upstreamed.

Based-on-patches-by: default avatarPetr Mladek <pmladek@suse.com>
Signed-off-by: default avatarJessica Yu <jeyu@kernel.org>
Acked-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: David S . Miller <davem@davemloft.net>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Joe Lawrence <joe.lawrence@redhat.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Miroslav Benes <mbenes@suse.cz>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: live-patching@vger.kernel.org
Link: http://lkml.kernel.org/r/20180109235124.30886-3-jeyu@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 12310e34

kernel/kprobes.c

+53 −25
Original line number Diff line number Diff line
@@ -1011,23 +1011,27 @@ err_ftrace: 
}



/* Caller must lock kprobe_mutex */

static void disarm_kprobe_ftrace(struct kprobe *p)

static int disarm_kprobe_ftrace(struct kprobe *p)

{

	int ret;

	int ret = 0;



	kprobe_ftrace_enabled--;

	if (kprobe_ftrace_enabled == 0) {

	if (kprobe_ftrace_enabled == 1) {

		ret = unregister_ftrace_function(&kprobe_ftrace_ops);

		WARN(ret < 0, "Failed to init kprobe-ftrace (%d)\n", ret);

		if (WARN(ret < 0, "Failed to unregister kprobe-ftrace (%d)\n", ret))

			return ret;

	}



	kprobe_ftrace_enabled--;



	ret = ftrace_set_filter_ip(&kprobe_ftrace_ops,

			   (unsigned long)p->addr, 1, 0);

	WARN(ret < 0, "Failed to disarm kprobe-ftrace at %p (%d)\n", p->addr, ret);

	return ret;

}

#else	/* !CONFIG_KPROBES_ON_FTRACE */

#define prepare_kprobe(p)	arch_prepare_kprobe(p)

#define arm_kprobe_ftrace(p)	(-ENODEV)

#define disarm_kprobe_ftrace(p)	do {} while (0)

#define disarm_kprobe_ftrace(p)	(-ENODEV)

#endif



/* Arm a kprobe with text_mutex */
@@ -1046,18 +1050,18 @@ static int arm_kprobe(struct kprobe *kp) 
}



/* Disarm a kprobe with text_mutex */

static void disarm_kprobe(struct kprobe *kp, bool reopt)

static int disarm_kprobe(struct kprobe *kp, bool reopt)

{

	if (unlikely(kprobe_ftrace(kp))) {

		disarm_kprobe_ftrace(kp);

		return;

	}

	if (unlikely(kprobe_ftrace(kp)))

		return disarm_kprobe_ftrace(kp);



	cpus_read_lock();

	mutex_lock(&text_mutex);

	__disarm_kprobe(kp, reopt);

	mutex_unlock(&text_mutex);

	cpus_read_unlock();



	return 0;

}



/*
@@ -1639,11 +1643,12 @@ static int aggr_kprobe_disabled(struct kprobe *ap) 
static struct kprobe *__disable_kprobe(struct kprobe *p)

{

	struct kprobe *orig_p;

	int ret;



	/* Get an original kprobe for return */

	orig_p = __get_valid_kprobe(p);

	if (unlikely(orig_p == NULL))

		return NULL;

		return ERR_PTR(-EINVAL);



	if (!kprobe_disabled(p)) {

		/* Disable probe if it is a child probe */
@@ -1657,8 +1662,13 @@ static struct kprobe *__disable_kprobe(struct kprobe *p) 
			 * should have already been disarmed, so

			 * skip unneed disarming process.

			 */

			if (!kprobes_all_disarmed)

				disarm_kprobe(orig_p, true);

			if (!kprobes_all_disarmed) {

				ret = disarm_kprobe(orig_p, true);

				if (ret) {

					p->flags &= ~KPROBE_FLAG_DISABLED;

					return ERR_PTR(ret);

				}

			}

			orig_p->flags |= KPROBE_FLAG_DISABLED;

		}

	}
@@ -1675,8 +1685,8 @@ static int __unregister_kprobe_top(struct kprobe *p) 


	/* Disable kprobe. This will disarm it if needed. */

	ap = __disable_kprobe(p);

	if (ap == NULL)

		return -EINVAL;

	if (IS_ERR(ap))

		return PTR_ERR(ap);



	if (ap == p)

		/*
@@ -2109,12 +2119,14 @@ static void kill_kprobe(struct kprobe *p) 
int disable_kprobe(struct kprobe *kp)

{

	int ret = 0;

	struct kprobe *p;



	mutex_lock(&kprobe_mutex);



	/* Disable this kprobe */

	if (__disable_kprobe(kp) == NULL)

		ret = -EINVAL;

	p = __disable_kprobe(kp);

	if (IS_ERR(p))

		ret = PTR_ERR(p);



	mutex_unlock(&kprobe_mutex);

	return ret;
@@ -2486,34 +2498,50 @@ already_enabled: 
	return ret;

}



static void disarm_all_kprobes(void)

static int disarm_all_kprobes(void)

{

	struct hlist_head *head;

	struct kprobe *p;

	unsigned int i;

	unsigned int i, total = 0, errors = 0;

	int err, ret = 0;



	mutex_lock(&kprobe_mutex);



	/* If kprobes are already disarmed, just return */

	if (kprobes_all_disarmed) {

		mutex_unlock(&kprobe_mutex);

		return;

		return 0;

	}



	kprobes_all_disarmed = true;

	printk(KERN_INFO "Kprobes globally disabled\n");



	for (i = 0; i < KPROBE_TABLE_SIZE; i++) {

		head = &kprobe_table[i];

		/* Disarm all kprobes on a best-effort basis */

		hlist_for_each_entry_rcu(p, head, hlist) {

			if (!arch_trampoline_kprobe(p) && !kprobe_disabled(p))

				disarm_kprobe(p, false);

			if (!arch_trampoline_kprobe(p) && !kprobe_disabled(p)) {

				err = disarm_kprobe(p, false);

				if (err) {

					errors++;

					ret = err;

				}

				total++;

			}

		}

	}



	if (errors)

		pr_warn("Kprobes globally disabled, but failed to disarm %d out of %d probes\n",

			errors, total);

	else

		pr_info("Kprobes globally disabled\n");



	mutex_unlock(&kprobe_mutex);



	/* Wait for disarming all kprobes by optimizer */

	wait_for_kprobe_optimizer();



	return ret;

}



/*
@@ -2556,7 +2584,7 @@ static ssize_t write_enabled_file_bool(struct file *file, 
	case 'n':

	case 'N':

	case '0':

		disarm_all_kprobes();

		ret = disarm_all_kprobes();

		break;

	default:

		return -EINVAL;

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