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>

5 files changed, 10 insertions, 0 deletions

diff --git a/sound/oss/au1550_ac97.c b/sound/oss/au1550_ac97.c
index 81e1f443d094..4191acccbcdb 100644
--- a/sound/oss/au1550_ac97.c
+++ b/sound/oss/au1550_ac97.c
@@ -1627,7 +1627,9 @@ au1550_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
                                     sizeof(abinfo)) ? -EFAULT : 0;
 
         case SNDCTL_DSP_NONBLOCK:
+                spin_lock(&file->f_lock);
                 file->f_flags |= O_NONBLOCK;
+                spin_unlock(&file->f_lock);
                 return 0;
 
         case SNDCTL_DSP_GETODELAY:
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:
diff --git a/sound/oss/sh_dac_audio.c b/sound/oss/sh_dac_audio.c
index e5d423994918..78cfb66e4c59 100644
--- a/sound/oss/sh_dac_audio.c
+++ b/sound/oss/sh_dac_audio.c
@@ -135,7 +135,9 @@ static int dac_audio_ioctl(struct inode *inode, struct file *file,
                 return put_user(AFMT_U8, (int *)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:
diff --git a/sound/oss/swarm_cs4297a.c b/sound/oss/swarm_cs4297a.c
index 41562ecde5bb..1edab7b4ea83 100644
--- a/sound/oss/swarm_cs4297a.c
+++ b/sound/oss/swarm_cs4297a.c
@@ -2200,7 +2200,9 @@ static int cs4297a_ioctl(struct inode *inode, struct file *file,
                                     sizeof(abinfo)) ? -EFAULT : 0;
 
         case SNDCTL_DSP_NONBLOCK:
+                spin_lock(&file->f_lock);
                 file->f_flags |= O_NONBLOCK;
+                spin_unlock(&file->f_lock);
                 return 0;
 
         case SNDCTL_DSP_GETODELAY:
diff --git a/sound/oss/vwsnd.c b/sound/oss/vwsnd.c
index 78b8acc7c3b9..187f72750e8f 100644
--- a/sound/oss/vwsnd.c
+++ b/sound/oss/vwsnd.c
@@ -2673,7 +2673,9 @@ static int vwsnd_audio_do_ioctl(struct inode *inode,
 
         case SNDCTL_DSP_NONBLOCK:       /* _SIO  ('P',14) */
                 DBGX("SNDCTL_DSP_NONBLOCK\n");
+                spin_lock(&file->f_lock);
                 file->f_flags |= O_NONBLOCK;
+                spin_unlock(&file->f_lock);
                 return 0;
 
         case SNDCTL_DSP_RESET:          /* _SIO  ('P', 0) */