[PATCH AUTOSEL 5.13 13/14] net: fix NULL pointer reference in cipso_v4_doi_free

[Dongliang Mu]

On Mon, Aug 30, 2021 at 8:01 PM Sasha Levin <sashal at kernel.org> wrote:
>
> From: 王贇 <yun.wang at linux.alibaba.com>
>
> [ Upstream commit 733c99ee8be9a1410287cdbb943887365e83b2d6 ]
>

Hi Sasha,

Michael Wang has sent a v2 patch [1] for this bug and it is merged
into netdev/net-next.git. However, the v1 patch is already in the
upstream tree.

How do you guys handle such a issue?

[1] https://lkml.org/lkml/2021/8/30/229

> 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' equal 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 for similar
> cases.
>
> Reported-by: Abaci <abaci at linux.alibaba.com>
> Signed-off-by: Michael Wang <yun.wang at linux.alibaba.com>
> Signed-off-by: David S. Miller <davem at davemloft.net>
> Signed-off-by: Sasha Levin <sashal at kernel.org>
> ---
>  net/ipv4/cipso_ipv4.c | 18 ++++++++++--------
>  1 file changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/net/ipv4/cipso_ipv4.c b/net/ipv4/cipso_ipv4.c
> index e0480c6cebaa..16bbd62db791 100644
> --- a/net/ipv4/cipso_ipv4.c
> +++ b/net/ipv4/cipso_ipv4.c
> @@ -466,14 +466,16 @@ void cipso_v4_doi_free(struct cipso_v4_doi *doi_def)
>         if (!doi_def)
>                 return;
>
> -       switch (doi_def->type) {
> -       case CIPSO_V4_MAP_TRANS:
> -               kfree(doi_def->map.std->lvl.cipso);
> -               kfree(doi_def->map.std->lvl.local);
> -               kfree(doi_def->map.std->cat.cipso);
> -               kfree(doi_def->map.std->cat.local);
> -               kfree(doi_def->map.std);
> -               break;
> +       if (doi_def->map.std) {
> +               switch (doi_def->type) {
> +               case CIPSO_V4_MAP_TRANS:
> +                       kfree(doi_def->map.std->lvl.cipso);
> +                       kfree(doi_def->map.std->lvl.local);
> +                       kfree(doi_def->map.std->cat.cipso);
> +                       kfree(doi_def->map.std->cat.local);
> +                       kfree(doi_def->map.std);
> +                       break;
> +               }
>         }
>         kfree(doi_def);
>  }
> --
> 2.30.2
>