Re: [PATCH] block: fix refcounting in BLKBSZSET

From: Tejun Heo
Date: Thu Feb 24 2011 - 09:56:01 EST

On Thu, Feb 24, 2011 at 03:48:33PM +0100, Miklos Szeredi wrote:
> [and lkml cc-d too]
> This fixes bug 29202 in the 2.6.38 regression list.
> Please apply.
> Thanks,
> Miklos
> ----
> Subject: block: fix refcounting in BLKBSZSET
> From: Miklos Szeredi <mszeredi@xxxxxxx>
> 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().
> Reported-by: Adam Kovari <kovariadam@xxxxxxxxx>
> CC: Tejun Heo <tj@xxxxxxxxxx>
> Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>

Ah, it was me after all. Sorry about that.

Acked-by: Tejun Heo <tj@xxxxxxxxxx>


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