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Tue, 14 Apr 2026 23:37:13 -0700 (PDT) Received: from TDC4045031631.e0cglfehwr0e5gttmepj3hi3hf.ux.internal.cloudapp.net ([20.63.37.123]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-50e1afebd48sm6222121cf.26.2026.04.14.23.37.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Apr 2026 23:37:13 -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, Ashutosh Desai Subject: [PATCH v3 net] ax25: fix OOB read after address header strip in ax25_rcv() Date: Wed, 15 Apr 2026 06:36:54 +0000 Message-Id: <20260415063654.3831353-1-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 remote station can send a crafted KISS frame that is just long enough to pass ax25_addr_parse() (minimum 14 address bytes) but carries no control or PID bytes. After ax25_kiss_rcv() strips the KISS framing byte and ax25_rcv() strips the address header with skb_pull(), skb->len drops to zero. The subsequent reads of skb->data[0] (control byte) and skb->data[1] (PID byte) are then out of bounds, which can crash the kernel or leak heap memory to a remote attacker. Use pskb_may_pull(skb, 2) after the skb_pull() to ensure both bytes are in the linear area before reading them. Discard malformed frames that carry no control/PID pair. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Ashutosh Desai --- V2 -> V3: remove incorrect Suggested-by; add symptom, Fixes, Cc stable V1 -> V2: use pskb_may_pull(skb, 2) instead of skb->len < 2 v2: https://lore.kernel.org/netdev/20260409152400.2219716-1-ashutoshdesai993@gmail.com/ v1: https://lore.kernel.org/netdev/20260409012235.2049389-1-ashutoshdesai993@gmail.com/ net/ax25/ax25_in.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/ax25/ax25_in.c b/net/ax25/ax25_in.c index d75b3e9ed93d..6a71dea876a1 100644 --- a/net/ax25/ax25_in.c +++ b/net/ax25/ax25_in.c @@ -217,6 +217,11 @@ static int ax25_rcv(struct sk_buff *skb, struct net_device *dev, */ skb_pull(skb, ax25_addr_size(&dp)); + if (!pskb_may_pull(skb, 2)) { + kfree_skb(skb); + return 0; + } + /* For our port addresses ? */ if (ax25cmp(&dest, dev_addr) == 0 && dp.lastrepeat + 1 == dp.ndigi) mine = 1; -- 2.34.1