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

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Date:   Thu, 26 Aug 2021 11:42:42 +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] 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' 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@...ux.alibaba.com>
Signed-off-by: Michael Wang <yun.wang@...ux.alibaba.com>
---

 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 099259f..7fbd0b5 100644
--- a/net/ipv4/cipso_ipv4.c
+++ b/net/ipv4/cipso_ipv4.c
@@ -465,14 +465,16 @@ 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);
 }
-- 
1.8.3.1