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Use f_lock to protect f_flags
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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 <[email protected]>
Cc: Al Viro <[email protected]>
Signed-off-by: Jonathan Corbet <[email protected]>
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Jonathan Corbet committed Mar 16, 2009
1 parent 6849991 commit db1dd4d
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Showing 13 changed files with 33 additions and 9 deletions.
5 changes: 2 additions & 3 deletions drivers/char/tty_io.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2162,13 +2162,12 @@ static int fionbio(struct file *file, int __user *p)
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;
}

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7 changes: 6 additions & 1 deletion drivers/usb/gadget/file_storage.c
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Expand Up @@ -1711,7 +1711,9 @@ static int do_write(struct fsg_dev *fsg)
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 */
Expand All @@ -1728,8 +1730,11 @@ static int do_write(struct fsg_dev *fsg)
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;
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2 changes: 2 additions & 0 deletions fs/fcntl.c
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Expand Up @@ -189,7 +189,9 @@ static int setfl(int fd, struct file * filp, unsigned long arg)
}
}

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;
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7 changes: 4 additions & 3 deletions fs/ioctl.c
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Original file line number Diff line number Diff line change
Expand Up @@ -404,10 +404,12 @@ static int ioctl_fionbio(struct file *filp, int __user *argp)
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;
}

Expand All @@ -432,10 +434,12 @@ static int ioctl_fioasync(unsigned int fd, struct file *filp,
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;
}

Expand Down Expand Up @@ -499,10 +503,7 @@ int do_vfs_ioctl(struct file *filp, unsigned int fd, unsigned int cmd,
break;

case FIONBIO:
/* BKL needed to avoid races tweaking f_flags */
lock_kernel();
error = ioctl_fionbio(filp, argp);
unlock_kernel();
break;

case FIOASYNC:
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5 changes: 4 additions & 1 deletion fs/nfsd/vfs.c
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Expand Up @@ -998,8 +998,11 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,

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);
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2 changes: 1 addition & 1 deletion include/linux/fs.h
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Expand Up @@ -848,7 +848,7 @@ struct file {
#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;
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2 changes: 2 additions & 0 deletions ipc/mqueue.c
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Expand Up @@ -1156,10 +1156,12 @@ SYSCALL_DEFINE3(mq_getsetattr, mqd_t, mqdes,
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;
}
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2 changes: 2 additions & 0 deletions sound/core/oss/pcm_oss.c
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Expand Up @@ -1895,7 +1895,9 @@ static int snd_pcm_oss_set_fragment(struct snd_pcm_oss_file *pcm_oss_file, unsig

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;
}

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2 changes: 2 additions & 0 deletions sound/oss/au1550_ac97.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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:
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2 changes: 2 additions & 0 deletions sound/oss/audio.c
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Expand Up @@ -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:
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2 changes: 2 additions & 0 deletions sound/oss/sh_dac_audio.c
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Expand Up @@ -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:
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2 changes: 2 additions & 0 deletions sound/oss/swarm_cs4297a.c
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Expand Up @@ -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:
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2 changes: 2 additions & 0 deletions sound/oss/vwsnd.c
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Expand Up @@ -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) */
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