| Message ID | 1380604559-5331-2-git-send-email-josh.durgin@inktank.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 10/01/2013 12:15 AM, Josh Durgin wrote: > get_user() and set_disk_ro() may allocate memory, leading to a > potential deadlock if theye are called while a spin lock is held. > > Move the acquisition and release of rbd_dev->lock from rbd_ioctl() > into rbd_ioctl_set_ro(), so it can occur between get_user() and > set_disk_ro(). This fix looks good. I have a couple small comments to consider. Reviewed-by: Alex Elder <elder@linaro.org> > Signed-off-by: Josh Durgin <josh.durgin@inktank.com> > --- > drivers/block/rbd.c | 36 +++++++++++++++++++++++------------- > 1 files changed, 23 insertions(+), 13 deletions(-) > > diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c > index 34bcdb7..b3b1b57 100644 > --- a/drivers/block/rbd.c > +++ b/drivers/block/rbd.c > @@ -510,23 +510,42 @@ static void rbd_release(struct gendisk *disk, fmode_t mode) > > static int rbd_ioctl_set_ro(struct rbd_device *rbd_dev, unsigned long arg) > { > + int ret = 0; > int val; > bool ro; > + bool ro_changed = false; > > + /* get_user() may sleep, so call it before taking rbd_dev->lock */ > if (get_user(val, (int __user *)(arg))) > return -EFAULT; > > + spin_lock_irq(&rbd_dev->lock); > + /* prevent others open this device */ > + if (rbd_dev->open_count > 1) { > + ret = -EBUSY; > + goto out; > + } I like to do as little as possible inside spinlock protection. > + > ro = val ? true : false; This assignment can be made outside the lock. > /* Snapshot doesn't allow to write*/ > - if (rbd_dev->spec->snap_id != CEPH_NOSNAP && !ro) > - return -EROFS; > + if (rbd_dev->spec->snap_id != CEPH_NOSNAP && !ro) { > + ret = -EROFS; > + goto out; > + } This check can be too. > > if (rbd_dev->mapping.read_only != ro) { > rbd_dev->mapping.read_only = ro; > - set_disk_ro(rbd_dev->disk, ro ? 1 : 0); > + ro_changed = true; > } > > - return 0; > +out: > + spin_unlock_irq(&rbd_dev->lock); > + /* set_disk_ro() may sleep, so call it after releasing rbd_dev->lock */ > + if (ret == 0 && ro_changed) > + set_disk_ro(rbd_dev->disk, ro ? 1 : 0); > + I like white space a lot, but this is one too many. > + > + return ret; > } > > static int rbd_ioctl(struct block_device *bdev, fmode_t mode, > @@ -535,13 +554,6 @@ static int rbd_ioctl(struct block_device *bdev, fmode_t mode, > struct rbd_device *rbd_dev = bdev->bd_disk->private_data; > int ret = 0; > > - spin_lock_irq(&rbd_dev->lock); > - /* prevent others open this device */ > - if (rbd_dev->open_count > 1) { > - ret = -EBUSY; > - goto out; > - } > - > switch (cmd) { > case BLKROSET: > ret = rbd_ioctl_set_ro(rbd_dev, arg); > @@ -550,8 +562,6 @@ static int rbd_ioctl(struct block_device *bdev, fmode_t mode, > ret = -ENOTTY; > } > > -out: > - spin_unlock_irq(&rbd_dev->lock); > return ret; > } > > -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index 34bcdb7..b3b1b57 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -510,23 +510,42 @@ static void rbd_release(struct gendisk *disk, fmode_t mode) static int rbd_ioctl_set_ro(struct rbd_device *rbd_dev, unsigned long arg) { + int ret = 0; int val; bool ro; + bool ro_changed = false; + /* get_user() may sleep, so call it before taking rbd_dev->lock */ if (get_user(val, (int __user *)(arg))) return -EFAULT; + spin_lock_irq(&rbd_dev->lock); + /* prevent others open this device */ + if (rbd_dev->open_count > 1) { + ret = -EBUSY; + goto out; + } + ro = val ? true : false; /* Snapshot doesn't allow to write*/ - if (rbd_dev->spec->snap_id != CEPH_NOSNAP && !ro) - return -EROFS; + if (rbd_dev->spec->snap_id != CEPH_NOSNAP && !ro) { + ret = -EROFS; + goto out; + } if (rbd_dev->mapping.read_only != ro) { rbd_dev->mapping.read_only = ro; - set_disk_ro(rbd_dev->disk, ro ? 1 : 0); + ro_changed = true; } - return 0; +out: + spin_unlock_irq(&rbd_dev->lock); + /* set_disk_ro() may sleep, so call it after releasing rbd_dev->lock */ + if (ret == 0 && ro_changed) + set_disk_ro(rbd_dev->disk, ro ? 1 : 0); + + + return ret; } static int rbd_ioctl(struct block_device *bdev, fmode_t mode, @@ -535,13 +554,6 @@ static int rbd_ioctl(struct block_device *bdev, fmode_t mode, struct rbd_device *rbd_dev = bdev->bd_disk->private_data; int ret = 0; - spin_lock_irq(&rbd_dev->lock); - /* prevent others open this device */ - if (rbd_dev->open_count > 1) { - ret = -EBUSY; - goto out; - } - switch (cmd) { case BLKROSET: ret = rbd_ioctl_set_ro(rbd_dev, arg); @@ -550,8 +562,6 @@ static int rbd_ioctl(struct block_device *bdev, fmode_t mode, ret = -ENOTTY; } -out: - spin_unlock_irq(&rbd_dev->lock); return ret; }
get_user() and set_disk_ro() may allocate memory, leading to a potential deadlock if theye are called while a spin lock is held. Move the acquisition and release of rbd_dev->lock from rbd_ioctl() into rbd_ioctl_set_ro(), so it can occur between get_user() and set_disk_ro(). Signed-off-by: Josh Durgin <josh.durgin@inktank.com> --- drivers/block/rbd.c | 36 +++++++++++++++++++++++------------- 1 files changed, 23 insertions(+), 13 deletions(-)