linux-kernel - Re: [PATCH] cifs: fix potential overflow in cifs_compose_mount

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Date:	Wed, 10 Feb 2016 18:14:21 -0600
From:	Steve French <smfrench@...il.com>
To:	Insu Yun <wuninsu@...il.com>
Cc:	Steve French <sfrench@...ba.org>,
	"linux-cifs@...r.kernel.org" <linux-cifs@...r.kernel.org>,
	samba-technical <samba-technical@...ts.samba.org>,
	LKML <linux-kernel@...r.kernel.org>, taesoo@...ech.edu,
	yeongjin.jang@...ech.edu, insu@...ech.edu, changwoo@...ech.edu
Subject: Re: [PATCH] cifs: fix potential overflow in cifs_compose_mount_options

On Mon, Feb 1, 2016 at 10:34 AM, Insu Yun <wuninsu@...il.com> wrote:
> In worst case, "ip=" + sb_mountdata + ipv6 can be copied into mountdata.
> Therefore, for safe, it is better to add more size when allocating memory.
>
> Signed-off-by: Insu Yun <wuninsu@...il.com>
> ---
>  fs/cifs/cifs_dfs_ref.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/cifs/cifs_dfs_ref.c b/fs/cifs/cifs_dfs_ref.c
> index 7dc886c..e956cba 100644
> --- a/fs/cifs/cifs_dfs_ref.c
> +++ b/fs/cifs/cifs_dfs_ref.c
> @@ -175,7 +175,7 @@ char *cifs_compose_mount_options(const char *sb_mountdata,
>          * string to the length of the original string to allow for worst case.
>          */
>         md_len = strlen(sb_mountdata) + INET6_ADDRSTRLEN;
> -       mountdata = kzalloc(md_len + 1, GFP_KERNEL);
> +       mountdata = kzalloc(md_len + sizeof("ip=") + 1, GFP_KERNEL);
>         if (mountdata == NULL) {
>                 rc = -ENOMEM;
>                 goto compose_mount_options_err;

Not likely to be reproducible in practice (since ip= is already in the
sb_mountdata) but in case mount.cifs was missing and ip= was missing from
the original mount string, might as well add it.

Merged into cifs-2.6.git


-- 
Thanks,

Steve