Re: [PATCH v4] xfs_db: release ip resource before returning from get_next_unlinked()

["Darrick J. Wong" <djwong@kernel.org>]

On Fri, Aug 09, 2024 at 11:15:11AM -0500, Bill O'Donnell wrote:
> Fix potential memory leak in function get_next_unlinked(). Call
> libxfs_irele(ip) before exiting.
> 
> Details:
> Error: RESOURCE_LEAK (CWE-772):
> xfsprogs-6.5.0/db/iunlink.c:51:2: alloc_arg: "libxfs_iget" allocates memory that is stored into "ip".
> xfsprogs-6.5.0/db/iunlink.c:68:2: noescape: Resource "&ip->i_imap" is not freed or pointed-to in "libxfs_imap_to_bp".
> xfsprogs-6.5.0/db/iunlink.c:76:2: leaked_storage: Variable "ip" going out of scope leaks the storage it points to.
> #   74|   	libxfs_buf_relse(ino_bp);
> #   75|
> #   76|-> 	return ret;
> #   77|   bad:
> #   78|   	dbprintf(_("AG %u agino %u: %s\n"), agno, agino, strerror(error));
> 
> Signed-off-by: Bill O'Donnell <bodonnel@redhat.com>
> ---
> v2: cover error case.
> v3: fix coverage to not release unitialized variable.
> v4: add logic to cover error case when ip is not attained.
> ---
> db/iunlink.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/db/iunlink.c b/db/iunlink.c
> index d87562e3..98d1effc 100644
> --- a/db/iunlink.c
> +++ b/db/iunlink.c
> @@ -49,8 +49,12 @@ get_next_unlinked(
>  
>  	ino = XFS_AGINO_TO_INO(mp, agno, agino);
>  	error = -libxfs_iget(mp, NULL, ino, 0, &ip);
> -	if (error)
> -		goto bad;
> +	if (error) {
> +		if (ip)
> +			goto bad_rele;

When does libxfs_iget return nonzero and a non-NULL ip?  Wouldn't 'goto
bad' suffice here?

--D

> +		else
> +			goto bad;
> +	}
>  
>  	if (verbose) {
>  		xfs_filblks_t	blocks, rtblks = 0;
> @@ -67,13 +71,16 @@ get_next_unlinked(
>  
>  	error = -libxfs_imap_to_bp(mp, NULL, &ip->i_imap, &ino_bp);
>  	if (error)
> -		goto bad;
> +		goto bad_rele;
>  
>  	dip = xfs_buf_offset(ino_bp, ip->i_imap.im_boffset);
>  	ret = be32_to_cpu(dip->di_next_unlinked);
>  	libxfs_buf_relse(ino_bp);
> +	libxfs_irele(ip);
>  
>  	return ret;
> +bad_rele:
> +	libxfs_irele(ip);
>  bad:
>  	dbprintf(_("AG %u agino %u: %s\n"), agno, agino, strerror(error));
>  	return NULLAGINO;
> -- 
> 2.46.0
> 
>