Commit 3c522ced authored Feb 24, 2011 by Miklos Szeredi Committed by Linus Torvalds Feb 24, 2011

block: fix refcounting in BLKBSZSET

Adam Kovari and others reported that disconnecting an USB drive with
an ntfs-3g filesystem would cause "kernel BUG at fs/inode.c:1421!" to
be triggered.

The BUG could be traced back to ioctl(BLKBSZSET), which would
erroneously decrement the refcount on the bdev.  This is because
blkdev_get() expects the refcount to be already incremented and either
returns success or decrements the refcount and returns an error.

The bug was introduced by e525fd89 (block: make blkdev_get/put()
handle exclusive access), which didn't take into account this behavior
of blkdev_get().

This fixes
  https://bugzilla.kernel.org/show_bug.cgi?id=29202


(and likely 29792 too)

Reported-by: Adam Kovari <kovariadam@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent dcace5ac

block/ioctl.c

+5 −3

Original line number	Original line	Diff line number	Diff line
	@@ -294,9 +294,11 @@ int blkdev_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd,
	return -EINVAL;		return -EINVAL;
	if (get_user(n, (int __user *) arg))		if (get_user(n, (int __user *) arg))
	return -EFAULT;		return -EFAULT;
	if (!(mode & FMODE_EXCL) &&		if (!(mode & FMODE_EXCL)) {
	blkdev_get(bdev, mode \| FMODE_EXCL, &bdev) < 0)		bdgrab(bdev);
			if (blkdev_get(bdev, mode \| FMODE_EXCL, &bdev) < 0)
	return -EBUSY;		return -EBUSY;
			}
	ret = set_blocksize(bdev, n);		ret = set_blocksize(bdev, n);
	if (!(mode & FMODE_EXCL))		if (!(mode & FMODE_EXCL))
	blkdev_put(bdev, mode \| FMODE_EXCL);		blkdev_put(bdev, mode \| FMODE_EXCL);

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