[PATCH] dm: support ioctls on mapped devices: fix with fake file

The new ioctl code passes the wrong file pointer to the underlying device.
No file pointer is available so make a temporary fake one.

ioctl_by_bdev() does set_fs(KERNEL_DS) so it's for ioctls originating
within the kernel and unsuitable here.  We are processing ioctls that
originated in userspace and mapping them to different devices.  Fixing the
existing callers that pass a NULL file struct and consolidating the
fake_file users are separate matters to solve in later patches.

Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 7 insertions, 1 deletions

diff --git a/drivers/md/dm-linear.c b/drivers/md/dm-linear.c
index 2a6bad451f86..00234909b3db 100644
--- a/drivers/md/dm-linear.c
+++ b/drivers/md/dm-linear.c
@@ -104,8 +104,14 @@ static int linear_ioctl(struct dm_target *ti, struct inode *inode,
 {
         struct linear_c *lc = (struct linear_c *) ti->private;
         struct block_device *bdev = lc->dev->bdev;
+        struct file fake_file = {};
+        struct dentry fake_dentry = {};
 
-        return blkdev_driver_ioctl(bdev->bd_inode, filp, bdev->bd_disk, cmd, arg);
+        fake_file.f_mode = lc->dev->mode;
+        fake_file.f_dentry = &fake_dentry;
+        fake_dentry.d_inode = bdev->bd_inode;
+
+        return blkdev_driver_ioctl(bdev->bd_inode, &fake_file, bdev->bd_disk, cmd, arg);
 }
 
 static struct target_type linear_target = {