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-rw-r--r--kernel/kmod.c23
1 files changed, 22 insertions, 1 deletions
diff --git a/kernel/kmod.c b/kernel/kmod.c
index a4bea97c75b6..81b4a27261b2 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -36,6 +36,7 @@
#include <linux/resource.h>
#include <linux/notifier.h>
#include <linux/suspend.h>
+#include <linux/rwsem.h>
#include <asm/uaccess.h>
#include <trace/events/module.h>
@@ -50,6 +51,7 @@ static struct workqueue_struct *khelper_wq;
static kernel_cap_t usermodehelper_bset = CAP_FULL_SET;
static kernel_cap_t usermodehelper_inheritable = CAP_FULL_SET;
static DEFINE_SPINLOCK(umh_sysctl_lock);
+static DECLARE_RWSEM(umhelper_sem);
#ifdef CONFIG_MODULES
@@ -275,6 +277,7 @@ static void __call_usermodehelper(struct work_struct *work)
* If set, call_usermodehelper_exec() will exit immediately returning -EBUSY
* (used for preventing user land processes from being created after the user
* land has been frozen during a system-wide hibernation or suspend operation).
+ * Should always be manipulated under umhelper_sem acquired for write.
*/
static int usermodehelper_disabled = 1;
@@ -293,6 +296,18 @@ static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq);
*/
#define RUNNING_HELPERS_TIMEOUT (5 * HZ)
+void read_lock_usermodehelper(void)
+{
+ down_read(&umhelper_sem);
+}
+EXPORT_SYMBOL_GPL(read_lock_usermodehelper);
+
+void read_unlock_usermodehelper(void)
+{
+ up_read(&umhelper_sem);
+}
+EXPORT_SYMBOL_GPL(read_unlock_usermodehelper);
+
/**
* usermodehelper_disable - prevent new helpers from being started
*/
@@ -300,8 +315,10 @@ int usermodehelper_disable(void)
{
long retval;
+ down_write(&umhelper_sem);
usermodehelper_disabled = 1;
- smp_mb();
+ up_write(&umhelper_sem);
+
/*
* From now on call_usermodehelper_exec() won't start any new
* helpers, so it is sufficient if running_helpers turns out to
@@ -314,7 +331,9 @@ int usermodehelper_disable(void)
if (retval)
return 0;
+ down_write(&umhelper_sem);
usermodehelper_disabled = 0;
+ up_write(&umhelper_sem);
return -EAGAIN;
}
@@ -323,7 +342,9 @@ int usermodehelper_disable(void)
*/
void usermodehelper_enable(void)
{
+ down_write(&umhelper_sem);
usermodehelper_disabled = 0;
+ up_write(&umhelper_sem);
}
/**