Re: [PATCH] xfsprogs: fix inode crash in xfs_repair

[Dave Chinner <david@fromorbit.com>]

On Tue, Aug 13, 2013 at 05:13:31PM -0500, Mark Tinguely wrote:
> Adding the lost+found in phase 6 could allocate an inode from
> a new inode chunk. That newly created chunk was not around in
> the scan phase, and is not in the avl tree which will result
> in a NULL dereference.
> 
> This patch adds the newly created inode chunk and inodes as if
> found in the scan phase.
> 
> Metadata dump available for future tests.
> 
> Signed-off-by: Mark Tinguely <tinguely@sgi.com>
> ---
>  repair/incore_ino.c |    2 +-
>  repair/phase6.c     |   15 +++++++++++++++
>  2 files changed, 16 insertions(+), 1 deletion(-)
> 
> Index: b/repair/incore_ino.c
> ===================================================================
> --- a/repair/incore_ino.c
> +++ b/repair/incore_ino.c
> @@ -700,7 +700,7 @@ get_inode_parent(ino_tree_node_t *irec,
>  	return(0LL);
>  }
>  
> -static void
> +void
>  alloc_ex_data(ino_tree_node_t *irec)
>  {
>  	parent_list_t 	*ptbl;
> Index: b/repair/phase6.c
> ===================================================================
> --- a/repair/phase6.c
> +++ b/repair/phase6.c
> @@ -930,6 +930,21 @@ mk_orphanage(xfs_mount_t *mp)
>  	irec = find_inode_rec(mp,
>  			XFS_INO_TO_AGNO(mp, ino),
>  			XFS_INO_TO_AGINO(mp, ino));
> +
> +	if (irec == NULL && XFS_INO_TO_AGNO(mp, ino) < mp->m_sb.sb_agcount &&
> +	    ip != NULL && ip->i_d.di_magic == XFS_DINODE_MAGIC) {

I don't understand this check.

We've already dereferenced ip several lines above to increment the
link count and get the inode number stored in ino, so the ip != NULL
is unnecessary.

We've just allocated the inode, so why would the magic number be
wrong? And why would the inode number lie in a non-existent
allocation group?

> +		/*
> +		 * add the newly allocated inode chunk to the avl tree.
> +		 */

I can see from the code we are allocating and irec, inserting it
into the AVL tree and marking all the inodes in the chunk as free.
The comment should explain *why* we need to do this.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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