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From:   Jia-Ju Bai <baijiaju1990@gmail.com>
To:     johannes@sipsolutions.net, kvalo@codeaurora.org,
        davem@davemloft.net
Cc:     linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, Jia-Ju Bai <baijiaju1990@gmail.com>
Subject: [PATCH] mac80211_hwsim: Fix possible null-pointer dereferences in hwsim_dump_radio_nl()
Date:   Mon, 29 Jul 2019 16:23:32 +0800
Message-Id: <20190729082332.28895-1-baijiaju1990@gmail.com>
Sender: linux-wireless-owner@vger.kernel.org
Precedence: bulk

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@gmail.com>
---
 drivers/net/wireless/mac80211_hwsim.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/mac80211_hwsim.c b/drivers/net/wireless/mac80211_hwsim.c
index 519b4ee88c5c..61a8b6429e09 100644
--- a/drivers/net/wireless/mac80211_hwsim.c
+++ b/drivers/net/wireless/mac80211_hwsim.c
@@ -3617,10 +3617,11 @@ 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:
-- 
2.17.0