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| author | Johannes Berg <johannes.berg@intel.com> | 2016-01-26 11:29:03 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-03-03 15:06:24 -0800 |
| commit | 01e527fd4c73d05125d04ce3bfd4413eb5af2581 (patch) | |
| tree | 7d6358398e7fec403bb256cd11866453b8be9e8a | |
| parent | eb80decbf08882c0dc6573d329fd9b5c1aff3c31 (diff) | |
| download | lwn-01e527fd4c73d05125d04ce3bfd4413eb5af2581.tar.gz lwn-01e527fd4c73d05125d04ce3bfd4413eb5af2581.zip | |
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>
| -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 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; } 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) |