Use f_lock to protect f_flags

Traditionally, changes to struct file->f_flags have been done under BKL
protection, or with no protection at all.  This patch causes all f_flags
changes after file open/creation time to be done under protection of
f_lock.  This allows the removal of some BKL usage and fixes a number of
longstanding (if microscopic) races.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/sound/oss/audio.c b/sound/oss/audio.c
index 89bd27a5e865..b69c05b7ea7b 100644
--- a/sound/oss/audio.c
+++ b/sound/oss/audio.c
@@ -433,7 +433,9 @@ int audio_ioctl(int dev, struct file *file, unsigned int cmd, void __user *arg)
                         return dma_ioctl(dev, cmd, arg);
                 
                 case SNDCTL_DSP_NONBLOCK:
+                        spin_lock(&file->f_lock);
                         file->f_flags |= O_NONBLOCK;
+                        spin_unlock(&file->f_lock);
                         return 0;
 
                 case SNDCTL_DSP_GETCAPS: