Commit 5c51543b authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Linus Torvalds
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kprobes: Fix a double lock bug of kprobe_mutex 



Fix a double locking bug caused when debug.kprobe-optimization=0.
While the proc_kprobes_optimization_handler locks kprobe_mutex,
wait_for_kprobe_optimizer locks it again and that causes a double lock.
To fix the bug, this introduces different mutex for protecting
sysctl parameter and locks it in proc_kprobes_optimization_handler.
Of course, since we need to lock kprobe_mutex when touching kprobes
resources, that is done in *optimize_all_kprobes().

This bug was introduced by commit ad72b3be ("kprobes: fix
wait_for_kprobe_optimizer()")

Signed-off-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: default avatarAnanth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d202f051

kernel/kprobes.c

+13 −6
Original line number Diff line number Diff line
@@ -794,16 +794,16 @@ out: 
}



#ifdef CONFIG_SYSCTL

/* This should be called with kprobe_mutex locked */

static void __kprobes optimize_all_kprobes(void)

{

	struct hlist_head *head;

	struct kprobe *p;

	unsigned int i;



	mutex_lock(&kprobe_mutex);

	/* If optimization is already allowed, just return */

	if (kprobes_allow_optimization)

		return;

		goto out;



	kprobes_allow_optimization = true;

	for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
@@ -813,18 +813,22 @@ static void __kprobes optimize_all_kprobes(void) 
				optimize_kprobe(p);

	}

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

out:

	mutex_unlock(&kprobe_mutex);

}



/* This should be called with kprobe_mutex locked */

static void __kprobes unoptimize_all_kprobes(void)

{

	struct hlist_head *head;

	struct kprobe *p;

	unsigned int i;



	mutex_lock(&kprobe_mutex);

	/* If optimization is already prohibited, just return */

	if (!kprobes_allow_optimization)

	if (!kprobes_allow_optimization) {

		mutex_unlock(&kprobe_mutex);

		return;

	}



	kprobes_allow_optimization = false;

	for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
@@ -834,11 +838,14 @@ static void __kprobes unoptimize_all_kprobes(void) 
				unoptimize_kprobe(p, false);

		}

	}

	mutex_unlock(&kprobe_mutex);



	/* Wait for unoptimizing completion */

	wait_for_kprobe_optimizer();

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

}



static DEFINE_MUTEX(kprobe_sysctl_mutex);

int sysctl_kprobes_optimization;

int proc_kprobes_optimization_handler(struct ctl_table *table, int write,

				      void __user *buffer, size_t *length,
@@ -846,7 +853,7 @@ int proc_kprobes_optimization_handler(struct ctl_table *table, int write, 
{

	int ret;



	mutex_lock(&kprobe_mutex);

	mutex_lock(&kprobe_sysctl_mutex);

	sysctl_kprobes_optimization = kprobes_allow_optimization ? 1 : 0;

	ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
@@ -854,7 +861,7 @@ int proc_kprobes_optimization_handler(struct ctl_table *table, int write, 
		optimize_all_kprobes();

	else

		unoptimize_all_kprobes();

	mutex_unlock(&kprobe_mutex);

	mutex_unlock(&kprobe_sysctl_mutex);



	return ret;

}

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