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>
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index bc84e12..224f271 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -2162,13 +2162,12 @@
if (get_user(nonblock, p))
return -EFAULT;
- /* file->f_flags is still BKL protected in the fs layer - vomit */
- lock_kernel();
+ spin_lock(&file->f_lock);
if (nonblock)
file->f_flags |= O_NONBLOCK;
else
file->f_flags &= ~O_NONBLOCK;
- unlock_kernel();
+ spin_unlock(&file->f_lock);
return 0;
}
diff --git a/drivers/usb/gadget/file_storage.c b/drivers/usb/gadget/file_storage.c
index 1ab9dac..33bb76c 100644
--- a/drivers/usb/gadget/file_storage.c
+++ b/drivers/usb/gadget/file_storage.c
@@ -1711,7 +1711,9 @@
curlun->sense_data = SS_WRITE_PROTECTED;
return -EINVAL;
}
+ spin_lock(&curlun->filp->f_lock);
curlun->filp->f_flags &= ~O_SYNC; // Default is not to wait
+ spin_unlock(&curlun->filp->f_lock);
/* Get the starting Logical Block Address and check that it's
* not too big */
@@ -1728,8 +1730,11 @@
curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
return -EINVAL;
}
- if (fsg->cmnd[1] & 0x08) // FUA
+ if (fsg->cmnd[1] & 0x08) { // FUA
+ spin_lock(&curlun->filp->f_lock);
curlun->filp->f_flags |= O_SYNC;
+ spin_unlock(&curlun->filp->f_lock);
+ }
}
if (lba >= curlun->num_sectors) {
curlun->sense_data = SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
diff --git a/fs/fcntl.c b/fs/fcntl.c
index bd215cc..04df857 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -189,7 +189,9 @@
}
}
+ spin_lock(&filp->f_lock);
filp->f_flags = (arg & SETFL_MASK) | (filp->f_flags & ~SETFL_MASK);
+ spin_unlock(&filp->f_lock);
out:
unlock_kernel();
return error;
diff --git a/fs/ioctl.c b/fs/ioctl.c
index 240ec639..421aab4 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -404,10 +404,12 @@
if (O_NONBLOCK != O_NDELAY)
flag |= O_NDELAY;
#endif
+ spin_lock(&filp->f_lock);
if (on)
filp->f_flags |= flag;
else
filp->f_flags &= ~flag;
+ spin_unlock(&filp->f_lock);
return error;
}
@@ -432,10 +434,12 @@
if (error)
return error;
+ spin_lock(&filp->f_lock);
if (on)
filp->f_flags |= FASYNC;
else
filp->f_flags &= ~FASYNC;
+ spin_unlock(&filp->f_lock);
return error;
}
@@ -499,10 +503,7 @@
break;
case FIONBIO:
- /* BKL needed to avoid races tweaking f_flags */
- lock_kernel();
error = ioctl_fionbio(filp, argp);
- unlock_kernel();
break;
case FIOASYNC:
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 6e50aaa..c165a64 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -998,8 +998,11 @@
if (!EX_ISSYNC(exp))
stable = 0;
- if (stable && !EX_WGATHER(exp))
+ if (stable && !EX_WGATHER(exp)) {
+ spin_lock(&file->f_lock);
file->f_flags |= O_SYNC;
+ spin_unlock(&file->f_lock);
+ }
/* Write the data. */
oldfs = get_fs(); set_fs(KERNEL_DS);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 2011600..7428c6d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -848,7 +848,7 @@
#define f_dentry f_path.dentry
#define f_vfsmnt f_path.mnt
const struct file_operations *f_op;
- spinlock_t f_lock; /* f_ep_links */
+ spinlock_t f_lock; /* f_ep_links, f_flags */
atomic_long_t f_count;
unsigned int f_flags;
fmode_t f_mode;
diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index 54b4077..a8ddadb 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -1156,10 +1156,12 @@
omqstat.mq_flags = filp->f_flags & O_NONBLOCK;
if (u_mqstat) {
audit_mq_getsetattr(mqdes, &mqstat);
+ spin_lock(&filp->f_lock);
if (mqstat.mq_flags & O_NONBLOCK)
filp->f_flags |= O_NONBLOCK;
else
filp->f_flags &= ~O_NONBLOCK;
+ spin_unlock(&filp->f_lock);
inode->i_atime = inode->i_ctime = CURRENT_TIME;
}
diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c
index 0a1798e..d4460f1 100644
--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -1895,7 +1895,9 @@
static int snd_pcm_oss_nonblock(struct file * file)
{
+ spin_lock(&file->f_lock);
file->f_flags |= O_NONBLOCK;
+ spin_unlock(&file->f_lock);
return 0;
}
diff --git a/sound/oss/au1550_ac97.c b/sound/oss/au1550_ac97.c
index 81e1f44..4191acc 100644
--- a/sound/oss/au1550_ac97.c
+++ b/sound/oss/au1550_ac97.c
@@ -1627,7 +1627,9 @@
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 89bd27a..b69c05b 100644
--- a/sound/oss/audio.c
+++ b/sound/oss/audio.c
@@ -433,7 +433,9 @@
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 e5d4239..78cfb66 100644
--- a/sound/oss/sh_dac_audio.c
+++ b/sound/oss/sh_dac_audio.c
@@ -135,7 +135,9 @@
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 41562ec..1edab7b 100644
--- a/sound/oss/swarm_cs4297a.c
+++ b/sound/oss/swarm_cs4297a.c
@@ -2200,7 +2200,9 @@
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 78b8acc..187f727 100644
--- a/sound/oss/vwsnd.c
+++ b/sound/oss/vwsnd.c
@@ -2673,7 +2673,9 @@
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) */
