Re: [PATCH v8 2/6] xfs: sanity check directory inode di_size

From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Amir Goldstein <amir73il@gmail.com>
Cc: Brian Foster <bfoster@redhat.com>, Christoph Hellwig <hch@lst.de>,
	linux-xfs@vger.kernel.org
Subject: Re: [PATCH v8 2/6] xfs: sanity check directory inode di_size
Date: Fri, 13 Jan 2017 22:28:10 -0800	[thread overview]
Message-ID: <20170114062810.GG14038@birch.djwong.org> (raw)
In-Reply-To: <1484123050-11064-3-git-send-email-amir73il@gmail.com>

On Wed, Jan 11, 2017 at 10:24:06AM +0200, Amir Goldstein wrote:
> This changes fixes an assertion hit when fuzzing on-disk
> i_mode values.
> 
> The easy case to fix is when changing an empty file
> i_mode to S_IFDIR. In this case, xfs_dinode_verify()
> detects an illegal zero size for directory and fails
> to load the inode structure from disk.
> 
> For the case of non empty file whose i_mode is changed
> to S_IFDIR, the ASSERT() statement in xfs_dir2_isblock()
> is replaced with return -EFSCORRUPTED, to avoid interacting
> with corrupted jusk also when XFS_DEBUG is disabled.
> 
> Suggested-by: Darrick J. Wong <darrick.wong@oracle.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> ---
>  fs/xfs/libxfs/xfs_dir2.c      | 3 ++-
>  fs/xfs/libxfs/xfs_inode_buf.c | 7 +++++--
>  2 files changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_dir2.c b/fs/xfs/libxfs/xfs_dir2.c
> index c58d72c..4f7913f 100644
> --- a/fs/xfs/libxfs/xfs_dir2.c
> +++ b/fs/xfs/libxfs/xfs_dir2.c
> @@ -631,7 +631,8 @@ xfs_dir2_isblock(
>  	if ((rval = xfs_bmap_last_offset(args->dp, &last, XFS_DATA_FORK)))
>  		return rval;
>  	rval = XFS_FSB_TO_B(args->dp->i_mount, last) == args->geo->blksize;
> -	ASSERT(rval == 0 || args->dp->i_d.di_size == args->geo->blksize);
> +	if (rval != 0 && args->dp->i_d.di_size != args->geo->blksize)
> +		return -EFSCORRUPTED;
>  	*vp = rval;
>  	return 0;
>  }
> diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
> index dd483e2..0091ac3 100644
> --- a/fs/xfs/libxfs/xfs_inode_buf.c
> +++ b/fs/xfs/libxfs/xfs_inode_buf.c
> @@ -386,6 +386,7 @@ xfs_dinode_verify(
>  	xfs_ino_t		ino,
>  	struct xfs_dinode	*dip)
>  {
> +	uint16_t		mode;
>  	uint16_t		flags;
>  	uint64_t		flags2;
>  
> @@ -396,8 +397,10 @@ xfs_dinode_verify(
>  	if (be64_to_cpu(dip->di_size) & (1ULL << 63))
>  		return false;
>  
> -	/* No zero-length symlinks. */
> -	if (S_ISLNK(be16_to_cpu(dip->di_mode)) && dip->di_size == 0)
> +	mode = be16_to_cpu(dip->di_mode);
> +
> +	/* No zero-length symlinks/dirs. */
> +	if ((S_ISLNK(mode) || S_ISDIR(mode)) && dip->di_size == 0)

Drat, I just hit this with the fuzzer tests, so I'll pull this in
for rc5.  Good work! :)

--D

>  		return false;
>  
>  	/* only version 3 or greater inodes are extensively verified here */
> -- 
> 2.7.4
> 
> --
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