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Thu, 16 Apr 2026 23:54:36 -0700 (PDT) Received: from TDC4045031631.e0cglfehwr0e5gttmepj3hi3hf.ux.internal.cloudapp.net ([20.63.37.123]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8e7d6ba19c3sm46771285a.21.2026.04.16.23.54.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 16 Apr 2026 23:54:35 -0700 (PDT) From: Ashutosh Desai To: netdev@vger.kernel.org Cc: linux-hams@vger.kernel.org, jreuter@yaina.de, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, stable@vger.kernel.org, linux-kernel@vger.kernel.org, david.laight.linux@gmail.com, Ashutosh Desai Subject: [PATCH v4 net] ax25: fix OOB read after address header strip in ax25_rcv() Date: Fri, 17 Apr 2026 06:54:07 +0000 Message-Id: <20260417065407.206499-1-ashutoshdesai993@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit A crafted AX.25 frame with a valid address header but no control or PID bytes causes skb->len to drop to zero after skb_pull() strips the address header. The subsequent reads of skb->data[0] and skb->data[1] are then out of bounds. Linearize the skb at entry to ax25_rcv() so all subsequent accesses to skb->data are safe. Then check skb->len before reading the control and PID bytes, discarding frames that are too short. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Ashutosh Desai --- v4: linearize skb at entry to ax25_rcv(); replace pskb_may_pull() with skb->len check v3: remove incorrect Suggested-by; add symptom, Fixes, Cc stable v2: use pskb_may_pull(skb, 2) instead of skb->len < 2 Link to v3: https://lore.kernel.org/netdev/20260415063654.3831353-1-ashutoshdesai993@gmail.com/ Link to v2: https://lore.kernel.org/netdev/20260409152400.2219716-1-ashutoshdesai993@gmail.com/ Link to v1: https://lore.kernel.org/netdev/20260409012235.2049389-1-ashutoshdesai993@gmail.com/ net/ax25/ax25_in.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/net/ax25/ax25_in.c b/net/ax25/ax25_in.c index d75b3e9ed93d..d14ccebf9cdd 100644 --- a/net/ax25/ax25_in.c +++ b/net/ax25/ax25_in.c @@ -190,6 +190,9 @@ static int ax25_rcv(struct sk_buff *skb, struct net_device *dev, ax25_cb *ax25; ax25_dev *ax25_dev; + if (skb_linearize(skb)) + goto free; + /* * Process the AX.25/LAPB frame. */ @@ -217,6 +220,9 @@ static int ax25_rcv(struct sk_buff *skb, struct net_device *dev, */ skb_pull(skb, ax25_addr_size(&dp)); + if (skb->len < 2) + goto free; + /* For our port addresses ? */ if (ax25cmp(&dest, dev_addr) == 0 && dp.lastrepeat + 1 == dp.ndigi) mine = 1; -- 2.34.1