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>
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 1c88fba..6423f6e 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -561,9 +561,12 @@
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 @@
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 @@
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 @@
ret = -ENOTTY;
}
-out:
- spin_unlock_irq(&rbd_dev->lock);
return ret;
}