block: move CAP_SYS_ADMIN check in blkdev_roset()

Check for CAP_SYS_ADMIN before calling into the driver, similar to
blkdev_flushbuf().  This is safer and can spare a check in the driver.

(Currently BLKROSET is overridden by md and rbd, rbd is missing the
check.  md has the check, but it covers a lot more than BLKROSET.)

Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 3 insertions, 2 deletions

diff --git a/block/ioctl.c b/block/ioctl.c
index c0fc32bd8ed1..1668506d8ed8 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -443,11 +443,12 @@ static int blkdev_roset(struct block_device *bdev, fmode_t mode,
 {
         int ret, n;
 
+        if (!capable(CAP_SYS_ADMIN))
+                return -EACCES;
+
         ret = __blkdev_driver_ioctl(bdev, mode, cmd, arg);
         if (!is_unrecognized_ioctl(ret))
                 return ret;
-        if (!capable(CAP_SYS_ADMIN))
-                return -EACCES;
         if (get_user(n, (int __user *)arg))
                 return -EFAULT;
         set_device_ro(bdev, n);