diff options
authorJohannes Berg <johannes.berg@intel.com>2016-01-26 11:29:03 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-03-03 15:06:24 -0800
commit01e527fd4c73d05125d04ce3bfd4413eb5af2581 (patch)
parenteb80decbf08882c0dc6573d329fd9b5c1aff3c31 (diff)
rfkill: fix rfkill_fop_read wait_event usage
commit 6736fde9672ff6717ac576e9bba2fd5f3dfec822 upstream. The code within wait_event_interruptible() is called with !TASK_RUNNING, so mustn't call any functions that can sleep, like mutex_lock(). Since we re-check the list_empty() in a loop after the wait, it's safe to simply use list_empty() without locking. This bug has existed forever, but was only discovered now because all userspace implementations, including the default 'rfkill' tool, use poll() or select() to get a readable fd before attempting to read. Fixes: c64fb01627e24 ("rfkill: create useful userspace interface") Reported-by: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Johannes Berg <johannes.berg@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 4 insertions, 12 deletions
diff --git a/net/rfkill/core.c b/net/rfkill/core.c
index e2e2e6154fd2..6563cc04c578 100644
--- a/net/rfkill/core.c
+++ b/net/rfkill/core.c
@@ -1088,17 +1088,6 @@ static unsigned int rfkill_fop_poll(struct file *file, poll_table *wait)
return res;
-static bool rfkill_readable(struct rfkill_data *data)
- bool r;
- mutex_lock(&data->mtx);
- r = !list_empty(&data->events);
- mutex_unlock(&data->mtx);
- return r;
static ssize_t rfkill_fop_read(struct file *file, char __user *buf,
size_t count, loff_t *pos)
@@ -1115,8 +1104,11 @@ static ssize_t rfkill_fop_read(struct file *file, char __user *buf,
goto out;
+ /* since we re-check and it just compares pointers,
+ * using !list_empty() without locking isn't a problem
+ */
ret = wait_event_interruptible(data->read_wait,
- rfkill_readable(data));
+ !list_empty(&data->events));
if (ret)