netdev - [PATCH] mac80211_hwsim: correctly handle zero length frames

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Message-Id: <20210610161916.9307-1-mail@anirudhrb.com>
Date:   Thu, 10 Jun 2021 21:49:16 +0530
From:   Anirudh Rayabharam <mail@...rudhrb.com>
To:     Johannes Berg <johannes@...solutions.net>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     gregkh@...uxfoundation.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        Anirudh Rayabharam <mail@...rudhrb.com>,
        syzbot+b2645b5bf1512b81fa22@...kaller.appspotmail.com,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] mac80211_hwsim: correctly handle zero length frames

syzbot, using KMSAN, has reported an uninit-value access in
hwsim_cloned_frame_received_nl(). This is happening because frame_data_len
is 0. The code doesn't detect this case and blindly tries to read the
frame's header.

Fix this by bailing out in case frame_data_len is 0.

Reported-by: syzbot+b2645b5bf1512b81fa22@...kaller.appspotmail.com
Tested-by: syzbot+b2645b5bf1512b81fa22@...kaller.appspotmail.com
Signed-off-by: Anirudh Rayabharam <mail@...rudhrb.com>
---
 drivers/net/wireless/mac80211_hwsim.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/mac80211_hwsim.c b/drivers/net/wireless/mac80211_hwsim.c
index 51ce767eaf88..ccfe40313109 100644
--- a/drivers/net/wireless/mac80211_hwsim.c
+++ b/drivers/net/wireless/mac80211_hwsim.c
@@ -3649,7 +3649,7 @@ static int hwsim_cloned_frame_received_nl(struct sk_buff *skb_2,
 	if (skb == NULL)
 		goto err;
 
-	if (frame_data_len > IEEE80211_MAX_DATA_LEN)
+	if (frame_data_len == 0 || frame_data_len > IEEE80211_MAX_DATA_LEN)
 		goto err;
 
 	/* Copy the data */
-- 
2.26.2