Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Wed, 31 May 2023 15:11:47 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     =?ISO-8859-1?Q?Lu=EDs?= Henriques <lhenriques@suse.de>
Cc:     =?ISO-8859-1?Q?Lu=EDs?= Henriques via Ocfs2-devel 
        <ocfs2-devel@oss.oracle.com>, Mark Fasheh <mark@fasheh.com>,
        Joel Becker <jlbec@evilplan.org>,
        Joseph Qi <joseph.qi@linux.alibaba.com>,
        Heming Zhao <heming.zhao@suse.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [Ocfs2-devel] [PATCH] ocfs2: check new file size on fallocate
 call
Message-Id: <20230531151147.3d98aa2fb1d7f659bccef37b@linux-foundation.org>
In-Reply-To: <20230529152645.32680-1-lhenriques@suse.de>
References: <20230529152645.32680-1-lhenriques@suse.de>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Mon, 29 May 2023 16:26:45 +0100 Lu=EDs Henriques via Ocfs2-devel <ocfs2-=
devel@oss.oracle.com> wrote:

> When changing a file size with fallocate() the new size isn't being
> checked.  In particular, the FSIZE ulimit isn't being checked, which makes
> fstest generic/228 fail.  Simply adding a call to inode_newsize_ok() fixes
> this issue.
>=20
> ...
>
> --- a/fs/ocfs2/file.c
> +++ b/fs/ocfs2/file.c
> @@ -2100,14 +2100,20 @@ static long ocfs2_fallocate(struct file *file, in=
t mode, loff_t offset,
>  	struct ocfs2_space_resv sr;
>  	int change_size =3D 1;
>  	int cmd =3D OCFS2_IOC_RESVSP64;
> +	int ret =3D 0;
> =20
>  	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
>  		return -EOPNOTSUPP;
>  	if (!ocfs2_writes_unwritten_extents(osb))
>  		return -EOPNOTSUPP;
> =20
> -	if (mode & FALLOC_FL_KEEP_SIZE)
> +	if (mode & FALLOC_FL_KEEP_SIZE) {
>  		change_size =3D 0;
> +	} else {
> +		ret =3D inode_newsize_ok(inode, offset + len);
> +		if (ret)
> +			return ret;
> +	}
> =20

So userspace can exceed rlimit(RLIMIT_FSIZE).

Do we think this flaw is serious enough to justify backporting the fix
into earlier -stable kernels?