linux-kernel - [PATCH AUTOSEL 4.19 24/68] mac80211_hwsim: Fix possible null-pointer dereferences in hwsim_dump_radio

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Date:   Tue, 13 Aug 2019 22:15:02 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Jia-Ju Bai <baijiaju1990@...il.com>,
        Johannes Berg <johannes.berg@...el.com>,
        Sasha Levin <sashal@...nel.org>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 24/68] mac80211_hwsim: Fix possible null-pointer dereferences in hwsim_dump_radio_nl()

From: Jia-Ju Bai <baijiaju1990@...il.com>

[ Upstream commit b55f3b841099e641bdb2701d361a4c304e2dbd6f ]

In hwsim_dump_radio_nl(), when genlmsg_put() on line 3617 fails, hdr is
assigned to NULL. Then hdr is used on lines 3622 and 3623:
    genl_dump_check_consistent(cb, hdr);
    genlmsg_end(skb, hdr);

Thus, possible null-pointer dereferences may occur.

To fix these bugs, hdr is used here when it is not NULL.

This bug is found by a static analysis tool STCheck written by us.

Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
Link: https://lore.kernel.org/r/20190729082332.28895-1-baijiaju1990@gmail.com
[put braces on all branches]
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/wireless/mac80211_hwsim.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/mac80211_hwsim.c b/drivers/net/wireless/mac80211_hwsim.c
index 7cd428c0af433..ce2dd06af62e8 100644
--- a/drivers/net/wireless/mac80211_hwsim.c
+++ b/drivers/net/wireless/mac80211_hwsim.c
@@ -3502,10 +3502,12 @@ static int hwsim_dump_radio_nl(struct sk_buff *skb,
 		hdr = genlmsg_put(skb, NETLINK_CB(cb->skb).portid,
 				  cb->nlh->nlmsg_seq, &hwsim_genl_family,
 				  NLM_F_MULTI, HWSIM_CMD_GET_RADIO);
-		if (!hdr)
+		if (hdr) {
+			genl_dump_check_consistent(cb, hdr);
+			genlmsg_end(skb, hdr);
+		} else {
 			res = -EMSGSIZE;
-		genl_dump_check_consistent(cb, hdr);
-		genlmsg_end(skb, hdr);
+		}
 	}
 
 done:
-- 
2.20.1