[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20160129182815.GB5224@linux.intel.com>
Date: Fri, 29 Jan 2016 11:28:15 -0700
From: Ross Zwisler <ross.zwisler@...ux.intel.com>
To: Christoph Hellwig <hch@...radead.org>
Cc: Ross Zwisler <ross.zwisler@...ux.intel.com>,
linux-kernel@...r.kernel.org,
Alexander Viro <viro@...iv.linux.org.uk>,
Andrew Morton <akpm@...ux-foundation.org>,
Dan Williams <dan.j.williams@...el.com>,
Dave Chinner <david@...morbit.com>, Jan Kara <jack@...e.com>,
Matthew Wilcox <willy@...ux.intel.com>,
linux-fsdevel@...r.kernel.org, linux-nvdimm@...1.01.org
Subject: Re: [PATCH 2/2] dax: fix bdev NULL pointer dereferences
On Thu, Jan 28, 2016 at 01:38:58PM -0800, Christoph Hellwig wrote:
> On Thu, Jan 28, 2016 at 12:35:04PM -0700, Ross Zwisler wrote:
> > There are a number of places in dax.c that look up the struct block_device
> > associated with an inode. Previously this was done by just using
> > inode->i_sb->s_bdev. This is correct for inodes that exist within the
> > filesystems supported by DAX (ext2, ext4 & XFS), but when running DAX
> > against raw block devices this value is NULL. This causes NULL pointer
> > dereferences when these block_device pointers are used.
>
> It's also wrong for an XFS file system with a RT device..
>
> > +#define DAX_BDEV(inode) (S_ISBLK(inode->i_mode) ? I_BDEV(inode) \
> > + : inode->i_sb->s_bdev)
>
> .. but this isn't going to fix it. You must use a bdev returned by
> get_blocks or a similar file system method.
I guess I need to go off and understand if we can have DAX mappings on such a
device. If we can, we may have a problem - we can get the block_device from
get_block() in I/O path and the various fault paths, but we don't have access
to get_block() when flushing via dax_writeback_mapping_range(). We avoid
needing it the normal case by storing the sector results from get_block() in
the radix tree.
/me is off to play with RT devices...
Powered by blists - more mailing lists