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rbd: move calls that may sleep out of spin lock range 

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>
Reviewed-by: Alex Elder <elder@linaro.org>
This commit is contained in:
Josh Durgin 2013-09-30 17:09:54 -07:00
parent 131fd9f6fc
commit 77f33c0373
1 changed files with 20 additions and 13 deletions
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33
drivers/block/rbd.c
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@ -561,9 +561,12 @@ 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;
@ -572,12 +575,25 @@ static int rbd_ioctl_set_ro(struct rbd_device *rbd_dev, unsigned long arg)
if (rbd_dev->spec->snap_id != CEPH_NOSNAP && !ro)
return -EROFS;
if (rbd_dev->mapping.read_only != ro) {
rbd_dev->mapping.read_only = ro;
set_disk_ro(rbd_dev->disk, ro ? 1 : 0);
spin_lock_irq(&rbd_dev->lock);
/* prevent others open this device */
if (rbd_dev->open_count > 1) {
ret = -EBUSY;
goto out;
}
return 0;
if (rbd_dev->mapping.read_only != ro) {
rbd_dev->mapping.read_only = ro;
ro_changed = true;
}
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,
@ -586,13 +602,6 @@ 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);
@ -601,8 +610,6 @@ static int rbd_ioctl(struct block_device *bdev, fmode_t mode,
ret = -ENOTTY;
}
out:
spin_unlock_irq(&rbd_dev->lock);
return ret;
}