Re: [PATCH 1/1] xfs: Fix Smatch warning in xfs_attr_node_get

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

On Tue, Jul 28, 2020 at 05:08:53PM -0700, Allison Collins wrote:
> Fix warning: variable dereferenced before check 'state' in
> xfs_attr_node_get.  If xfs_attr_node_hasname fails, it may return a null
> state.  If state is null, do not derefrence it.  Go straight to out.
> 
> Signed-off-by: Allison Collins <allison.henderson@oracle.com>
> ---
>  fs/xfs/libxfs/xfs_attr.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> index e5ec9ed..90b7b24 100644
> --- a/fs/xfs/libxfs/xfs_attr.c
> +++ b/fs/xfs/libxfs/xfs_attr.c
> @@ -1409,6 +1409,9 @@ xfs_attr_node_get(
>  	 * Search to see if name exists, and get back a pointer to it.
>  	 */
>  	error = xfs_attr_node_hasname(args, &state);
> +	if (!state)
> +		goto out;
> +
>  	if (error != -EEXIST)
>  		goto out_release;
>  
> @@ -1426,7 +1429,7 @@ xfs_attr_node_get(

I would've just changed the for loop to:

	for (i = 0; state && i < state->path.active; i++) {

Since that way we'd know that the error-out path always does the right
thing wrt any resources that could have been allocated.

--D

>  		xfs_trans_brelse(args->trans, state->path.blk[i].bp);
>  		state->path.blk[i].bp = NULL;
>  	}
> -
> +out:
>  	if (state)
>  		xfs_da_state_free(state);
>  	return error;
> -- 
> 2.7.4
>