linux-kernel - Re: [PATCH v2] net: fix NULL pointer reference in cipso_v4_doi

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Date:   Mon, 30 Aug 2021 10:17:05 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     王贇 <yun.wang@...ux.alibaba.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] net: fix NULL pointer reference in cipso_v4_doi_free

On Mon, Aug 30, 2021 at 6:28 AM 王贇 <yun.wang@...ux.alibaba.com> wrote:
>
> In netlbl_cipsov4_add_std() when 'doi_def->map.std' alloc
> failed, we sometime observe panic:
>
>   BUG: kernel NULL pointer dereference, address:
>   ...
>   RIP: 0010:cipso_v4_doi_free+0x3a/0x80
>   ...
>   Call Trace:
>    netlbl_cipsov4_add_std+0xf4/0x8c0
>    netlbl_cipsov4_add+0x13f/0x1b0
>    genl_family_rcv_msg_doit.isra.15+0x132/0x170
>    genl_rcv_msg+0x125/0x240
>
> This is because in cipso_v4_doi_free() there is no check
> on 'doi_def->map.std' when doi_def->type got value 1, which
> is possibe, since netlbl_cipsov4_add_std() haven't initialize
> it before alloc 'doi_def->map.std'.
>
> This patch just add the check to prevent panic happen in similar
> cases.
>
> Reported-by: Abaci <abaci@...ux.alibaba.com>
> Signed-off-by: Michael Wang <yun.wang@...ux.alibaba.com>
> ---
>  net/netlabel/netlabel_cipso_v4.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

I see this was already merged, but it looks good to me, thanks for
making those changes.

> diff --git a/net/netlabel/netlabel_cipso_v4.c b/net/netlabel/netlabel_cipso_v4.c
> index baf2357..344c228 100644
> --- a/net/netlabel/netlabel_cipso_v4.c
> +++ b/net/netlabel/netlabel_cipso_v4.c
> @@ -144,8 +144,8 @@ static int netlbl_cipsov4_add_std(struct genl_info *info,
>                 return -ENOMEM;
>         doi_def->map.std = kzalloc(sizeof(*doi_def->map.std), GFP_KERNEL);
>         if (doi_def->map.std == NULL) {
> -               ret_val = -ENOMEM;
> -               goto add_std_failure;
> +               kfree(doi_def);
> +               return -ENOMEM;
>         }
>         doi_def->type = CIPSO_V4_MAP_TRANS;
>
> --
> 1.8.3.1

-- 
paul moore
www.paul-moore.com