netdev - [PATCH AUTOSEL 4.19 7/8] net: fix NULL pointer reference in cipso_v4_doi

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Date:   Mon, 30 Aug 2021 08:00:30 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     王贇 <yun.wang@...ux.alibaba.com>,
        Abaci <abaci@...ux.alibaba.com>,
        "David S . Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>, netdev@...r.kernel.org,
        linux-security-module@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 7/8] net: fix NULL pointer reference in cipso_v4_doi_free

From: 王贇 <yun.wang@...ux.alibaba.com>

[ Upstream commit 733c99ee8be9a1410287cdbb943887365e83b2d6 ]

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>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.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 e8b8dd1cb157..7372ba2659df 100644
--- a/net/ipv4/cipso_ipv4.c
+++ b/net/ipv4/cipso_ipv4.c
@@ -480,14 +480,16 @@ 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