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 ad72b3bea744 ("kprobes: fix
wait_for_kprobe_optimizer()")
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: Ananth 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: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index e35be53..3fed7f0 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -794,16 +794,16 @@
}
#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 @@
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 @@
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 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 @@
optimize_all_kprobes();
else
unoptimize_all_kprobes();
- mutex_unlock(&kprobe_mutex);
+ mutex_unlock(&kprobe_sysctl_mutex);
return ret;
}
