path: root/net
diff options
authorJohannes Berg <johannes.berg@intel.com>2016-01-26 11:29:03 +0100
committerJohannes Berg <johannes.berg@intel.com>2016-01-26 11:32:05 +0100
commit6736fde9672ff6717ac576e9bba2fd5f3dfec822 (patch)
tree744a387ea6c9555b197842db8e87cd538ddfc958 /net
parent4fa11ec726a32ea6dd768dbb2e2af3453a98ec0a (diff)
rfkill: fix rfkill_fop_read wait_event usage
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. Cc: stable@vger.kernel.org Fixes: c64fb01627e24 ("rfkill: create useful userspace interface") Reported-by: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Diffstat (limited to 'net')
1 files changed, 4 insertions, 12 deletions
diff --git a/net/rfkill/core.c b/net/rfkill/core.c
index f53bf3b6558b..cf5b69ab1829 100644
--- a/net/rfkill/core.c
+++ b/net/rfkill/core.c
@@ -1095,17 +1095,6 @@ 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)
@@ -1122,8 +1111,11 @@ 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)