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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Larry Finger <Larry.Finger@lwfinger.net>,
        Kalle Valo <kvalo@codeaurora.org>
Subject: [PATCH 5.3 130/163] rtlwifi: rtl_pci: Fix problem of too small skb->len
Date:   Mon,  4 Nov 2019 22:45:20 +0100
Message-Id: <20191104212149.737476048@linuxfoundation.org>
In-Reply-To: <20191104212140.046021995@linuxfoundation.org>
References: <20191104212140.046021995@linuxfoundation.org>
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From: Larry Finger <Larry.Finger@lwfinger.net>

commit b43f4a169f220e459edf3ea8f8cd3ec4ae7fa82d upstream.

In commit 8020919a9b99 ("mac80211: Properly handle SKB with radiotap
only"), buffers whose length is too short cause a WARN_ON(1) to be
executed. This change exposed a fault in rtlwifi drivers, which is fixed
by regarding packets with skb->len <= FCS_LEN as though they are in error
and dropping them. The test is now annotated as likely.

Cc: Stable <stable@vger.kernel.org> # v5.0+
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/net/wireless/realtek/rtlwifi/pci.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/net/wireless/realtek/rtlwifi/pci.c
+++ b/drivers/net/wireless/realtek/rtlwifi/pci.c
@@ -822,7 +822,7 @@ static void _rtl_pci_rx_interrupt(struct
 		hdr = rtl_get_hdr(skb);
 		fc = rtl_get_fc(skb);
 
-		if (!stats.crc && !stats.hwerror) {
+		if (!stats.crc && !stats.hwerror && (skb->len > FCS_LEN)) {
 			memcpy(IEEE80211_SKB_RXCB(skb), &rx_status,
 			       sizeof(rx_status));
 
@@ -859,6 +859,7 @@ static void _rtl_pci_rx_interrupt(struct
 				_rtl_pci_rx_to_mac80211(hw, skb, rx_status);
 			}
 		} else {
+			/* drop packets with errors or those too short */
 			dev_kfree_skb_any(skb);
 		}
 new_trx_end: