Input: sysrq - add locking to sysrq_filter()

Similarly to the keyboard handler, we are called by different input
devices and thus need to add spinlock if we want to maintain our
state properly.

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

1 files changed, 12 insertions, 3 deletions

diff --git a/drivers/char/sysrq.c b/drivers/char/sysrq.c
index ef31bb81e843..f0ad694cc2eb 100644
--- a/drivers/char/sysrq.c
+++ b/drivers/char/sysrq.c
@@ -566,10 +566,16 @@ static const unsigned char sysrq_xlate[KEY_MAX + 1] =
 static bool sysrq_down;
 static int sysrq_alt_use;
 static int sysrq_alt;
+static DEFINE_SPINLOCK(sysrq_event_lock);
 
 static bool sysrq_filter(struct input_handle *handle, unsigned int type,
                          unsigned int code, int value)
 {
+        bool suppress;
+
+        /* We are called with interrupts disabled, just take the lock */
+        spin_lock(&sysrq_event_lock);
+
         if (type != EV_KEY)
                 goto out;
 
@@ -601,7 +607,10 @@ static bool sysrq_filter(struct input_handle *handle, unsigned int type,
         }
 
 out:
-        return sysrq_down;
+        suppress = sysrq_down;
+        spin_unlock(&sysrq_event_lock);
+
+        return suppress;
 }
 
 static int sysrq_connect(struct input_handler *handler,
@@ -652,8 +661,8 @@ static void sysrq_disconnect(struct input_handle *handle)
 }
 
 /*
- * We are matching on KEY_LEFTALT insteard of KEY_SYSRQ because not all
- * keyboards have SysRq ikey predefined and so user may add it to keymap
+ * We are matching on KEY_LEFTALT instead of KEY_SYSRQ because not all
+ * keyboards have SysRq key predefined and so user may add it to keymap
  * later, but we expect all such keyboards to have left alt.
  */
 static const struct input_device_id sysrq_ids[] = {