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[85.86.63.67]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47fd45a1240sm7477683f8f.36.2026.07.31.11.33.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 31 Jul 2026 11:33:35 -0700 (PDT) Date: Fri, 31 Jul 2026 20:33:34 +0200 From: Pablo =?iso-8859-1?Q?Vallesp=EDn?= Aranguren To: Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , "open list:TULIP NETWORK DRIVERS" , "open list:TULIP NETWORK DRIVERS" , open list Cc: Greg KH Subject: [PATCH] net: tulip: xircom_cb: drop runt frames before skb copy Message-ID: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit investigate_read_descriptor() takes the 11-bit packet length straight from the device-written descriptor and subtracts 4 for the CRC. A length below 4 underflows pkt_len to a negative value, which is then passed to skb_put_data() as a huge unsigned length and corrupts memory past the end of the freshly allocated skb. Drop the frame as a length error if pkt_len is negative after CRC removal. Signed-off-by: Pablo Vallespín Aranguren Assisted-by: gkh_clanker_t1000 --- drivers/net/ethernet/dec/tulip/xircom_cb.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/net/ethernet/dec/tulip/xircom_cb.c b/drivers/net/ethernet/dec/tulip/xircom_cb.c index e5d2ede13845..62c64da1c8fa 100644 --- a/drivers/net/ethernet/dec/tulip/xircom_cb.c +++ b/drivers/net/ethernet/dec/tulip/xircom_cb.c @@ -1110,6 +1110,11 @@ investigate_read_descriptor(struct net_device *dev, struct xircom_private *card, /* minus 4, we don't want the CRC */ struct sk_buff *skb; + if (pkt_len < 0) { + dev->stats.rx_length_errors++; + goto out; + } + if (pkt_len > 1518) { netdev_err(dev, "Packet length %i is bogus\n", pkt_len); pkt_len = 1518; -- 2.55.0