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Date: Thu, 9 Apr 2026 01:22:35 +0000 Message-Id: <20260409012235.2049389-1-ashutoshdesai993@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" ax25_rcv() calls skb_pull(skb, ax25_addr_size(&dp)) to strip the address header, then immediately reads skb->data[0] and skb->data[1] without verifying the buffer still contains at least 2 bytes. A crafted 15-byte KISS frame (1 KISS byte + 14 address bytes with EBIT set in the source address, no control/PID bytes) passes ax25_addr_parse() which only requires len >=3D 14, and passes the KISS byte check (low nibble =3D=3D 0). After skb_pull(1) in ax25_kiss_rcv() and skb_pull(14) in ax25_rcv(), skb->len is 0 and the subsequent reads of skb->data[0] (control byte) and skb->data[1] (PID byte) are out of bounds. Add a check that at least 2 bytes remain after stripping the address header, freeing the skb and returning on malformed input. Signed-off-by: Ashutosh Desai --- 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 d75b3e9ed..92baac77f 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_de= vice *dev, */ skb_pull(skb, ax25_addr_size(&dp)); =20 + if (skb->len < 2) { + kfree_skb(skb); + return 0; + } + /* For our port addresses ? */ if (ax25cmp(&dest, dev_addr) =3D=3D 0 && dp.lastrepeat + 1 =3D=3D dp.ndig= i) mine =3D 1; --=20 2.34.1