linux-kernel - Re: [PATCH V2] xfs: fix string handling in get/set functions

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Date:   Wed, 6 Jun 2018 03:58:17 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Eric Sandeen <sandeen@...deen.net>
Cc:     Arnd Bergmann <arnd@...db.de>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        linux-xfs@...r.kernel.org, Eric Sandeen <sandeen@...hat.com>,
        Martin Sebor <msebor@...il.com>,
        Brian Foster <bfoster@...hat.com>,
        Dave Chinner <dchinner@...hat.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] xfs: fix string handling in get/set functions

> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> index 82f7c83c1dad..596e176c19a6 100644
> --- a/fs/xfs/xfs_ioctl.c
> +++ b/fs/xfs/xfs_ioctl.c
> @@ -1828,13 +1828,13 @@ xfs_ioc_getlabel(
>  	/* Paranoia */
>  	BUILD_BUG_ON(sizeof(sbp->sb_fname) > FSLABEL_MAX);
>  
> +	/* 1 larger than sb_fname, so this ensures a trailing NUL char */
> +	memset(label, 0, sizeof(label));

I don't get the comment.  In fact I don't even get why we need any
comment here.  This is a structure that gets copied to userspace,
and we zero the whole structure, as we should do by default for
anything that goes to userspace.

Otherwise this looks fine to me.