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| author | Johannes Berg <johannes.berg@intel.com> | 2016-01-26 11:29:03 +0100 |
|---|---|---|
| committer | Johannes Berg <johannes.berg@intel.com> | 2016-01-26 11:32:05 +0100 |
| commit | 6736fde9672ff6717ac576e9bba2fd5f3dfec822 (patch) | |
| tree | 744a387ea6c9555b197842db8e87cd538ddfc958 /net/rfkill | |
| parent | 4fa11ec726a32ea6dd768dbb2e2af3453a98ec0a (diff) | |
| download | lwn-6736fde9672ff6717ac576e9bba2fd5f3dfec822.tar.gz lwn-6736fde9672ff6717ac576e9bba2fd5f3dfec822.zip | |
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/rfkill')
| -rw-r--r-- | net/rfkill/core.c | 16 |
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; } mutex_unlock(&data->mtx); + /* 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)); mutex_lock(&data->mtx); if (ret) |