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From:   Paul Moore <paul@paul-moore.com>
Date:   Mon, 30 Aug 2021 10:17:05 -0400
Message-ID: <CAHC9VhTEs9E+ZeGGp96NnOhmr-6MZLXf6ckHeG8w5jh3AfgKiQ@mail.gmail.com>
Subject: Re: [PATCH v2] net: fix NULL pointer reference in cipso_v4_doi_free
To:     =?UTF-8?B?546L6LSH?= <yun.wang@linux.alibaba.com>
Cc:     "David S. Miller" <davem@davemloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        David Ahern <dsahern@kernel.org>,
        Jakub Kicinski <kuba@kernel.org>, netdev@vger.kernel.org,
        linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org
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On Mon, Aug 30, 2021 at 6:28 AM =E7=8E=8B=E8=B4=87 <yun.wang@linux.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@linux.alibaba.com>
> Signed-off-by: Michael Wang <yun.wang@linux.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_cip=
so_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 *i=
nfo,
>                 return -ENOMEM;
>         doi_def->map.std =3D kzalloc(sizeof(*doi_def->map.std), GFP_KERNE=
L);
>         if (doi_def->map.std =3D=3D NULL) {
> -               ret_val =3D -ENOMEM;
> -               goto add_std_failure;
> +               kfree(doi_def);
> +               return -ENOMEM;
>         }
>         doi_def->type =3D CIPSO_V4_MAP_TRANS;
>
> --
> 1.8.3.1

--=20
paul moore
www.paul-moore.com