netdev - [PATCH v2] net: fix NULL pointer reference in cipso_v4_doi

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Date:   Mon, 30 Aug 2021 18:28:01 +0800
From:   王贇 <yun.wang@...ux.alibaba.com>
To:     Paul Moore <paul@...l-moore.com>,
        "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: [PATCH v2] net: fix NULL pointer reference in cipso_v4_doi_free

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(-)

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