Re: [PATCH V2] xfs: Initialize variables in xfs_alloc_get_rec before using them

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Thu, Jun 28, 2018 at 11:28:35AM +0200, Carlos Maiolino wrote:
> Make sure we initialize *bno and *len, before jumping to out_bad_rec
> label, and risk calling xfs_warn() with uninitialized variables.
> 
> Coverity: 100898
> Coverity: 1437081
> Coverity: 1437129
> Coverity: 1437191
> Coverity: 1437201
> Coverity: 1437212
> Coverity: 1437341
> Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>

Looks ok,
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

> ---
> 
> This is based on Darrick's suggestion, although, I believe initializing *bno and
> *len before testing if *len is empty or not is a bit more clear than changing
> xfs_warn() to use rec->alloc.ar_startblock and rec->alloc.ar_blockcount
> directly.
> 
>  fs/xfs/libxfs/xfs_alloc.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
> index eef466260d43..75dbdc14c45f 100644
> --- a/fs/xfs/libxfs/xfs_alloc.c
> +++ b/fs/xfs/libxfs/xfs_alloc.c
> @@ -223,12 +223,13 @@ xfs_alloc_get_rec(
>  	error = xfs_btree_get_rec(cur, &rec, stat);
>  	if (error || !(*stat))
>  		return error;
> -	if (rec->alloc.ar_blockcount == 0)
> -		goto out_bad_rec;
>  
>  	*bno = be32_to_cpu(rec->alloc.ar_startblock);
>  	*len = be32_to_cpu(rec->alloc.ar_blockcount);
>  
> +	if (*len == 0)
> +		goto out_bad_rec;
> +
>  	/* check for valid extent range, including overflow */
>  	if (!xfs_verify_agbno(mp, agno, *bno))
>  		goto out_bad_rec;
> -- 
> 2.14.3
> 
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