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charset="utf-8" The BPQ length field is decoded as: len =3D skb->data[0] + skb->data[1] * 256 - 5; If the sender sets bytes [0..1] to values whose combined value is less than 5, len becomes negative. Passing a negative int to skb_trim() silently converts to a huge unsigned value, causing the function to be a no-op. The frame is then passed up to AX.25 with its original (untrimmed) payload, delivering garbage beyond the declared frame boundary. Additionally, a negative len corrupts the 64-bit rx_bytes counter through implicit sign-extension. Add a bounds check before pulling the length bytes: reject frames where len is negative or exceeds the remaining skb data. Cc: stable@vger.kernel.org Cc: linux-hams@vger.kernel.org Acked-by: Joerg Reuter Signed-off-by: Mashiro Chen --- drivers/net/hamradio/bpqether.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/net/hamradio/bpqether.c b/drivers/net/hamradio/bpqethe= r.c index 045c5177262eaf..214fd1f819a1bb 100644 --- a/drivers/net/hamradio/bpqether.c +++ b/drivers/net/hamradio/bpqether.c @@ -187,6 +187,9 @@ static int bpq_rcv(struct sk_buff *skb, struct net_devi= ce *dev, struct packet_ty =20 len =3D skb->data[0] + skb->data[1] * 256 - 5; =20 + if (len < 0 || len > skb->len - 2) + goto drop_unlock; + skb_pull(skb, 2); /* Remove the length bytes */ skb_trim(skb, len); /* Set the length of the data */ =20 --=20 2.53.0 From nobody Mon Jun 15 07:34:00 2026 Received: from mout-y-209.mailbox.org (mout-y-209.mailbox.org [91.198.250.237]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0421136215B; 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t=1775703010; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Ca/hCivNQ+GfsLCWu5A+fqrBPvC83j+aR85nKjfB7dw=; b=dDL0bvUWqixxzImVwTQW3s6pSadl+H8bX66XM/cBycE7ropjpUUEn4ABPu+/7YHquTXo6m Y0uVAtPUQ+C1X3AeAvX7ACDyFaE0qjX7NDoCXAt/tKTLbWNOdOnbKyI4RfoXzaMjNEm9A7 RR7/73nAkVakCgSJXPjd2Ap/DBo7O7jM6u8XiWpg2U2VPNFklH9FsgcHIoPZez5iv+nmTS vYaRGp9jMRcw021wTPzAzbBZY2SKT1SqD2f+y4vYRX+dNQ0pT2iZCcEXauq9+rgPzf8fvK CRtaRv1P0mzIdRqUsSBqSt8VvmL24AldzHkW7qixPBnVu2ZwwaHX/DvtoKuIPA== To: netdev@vger.kernel.org Cc: andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, jreuter@yaina.de, linux-hams@vger.kernel.org, linux-kernel@vger.kernel.org, Mashiro Chen , stable@vger.kernel.org Subject: [PATCH v2 net 2/2] net: hamradio: scc: validate bufsize in SIOCSCCSMEM ioctl Date: Thu, 9 Apr 2026 10:49:27 +0800 Message-ID: <20260409024927.24397-3-mashiro.chen@mailbox.org> In-Reply-To: <20260409024927.24397-1-mashiro.chen@mailbox.org> References: <20260409024927.24397-1-mashiro.chen@mailbox.org> 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 X-MBO-RS-ID: f6290bd8d58f4ba352a X-MBO-RS-META: 3e56zqrj9h4snafz64i6ixnrmmbcwrkd X-Rspamd-Queue-Id: 4frktr23rGzB14V Content-Type: text/plain; charset="utf-8" The SIOCSCCSMEM ioctl copies a scc_mem_config from user space and assigns its bufsize field directly to scc->stat.bufsize without any range validation: scc->stat.bufsize =3D memcfg.bufsize; If a privileged user (CAP_SYS_RAWIO) sets bufsize to 0, the receive interrupt handler later calls dev_alloc_skb(0) and immediately writes a KISS type byte via skb_put_u8() into a zero-capacity socket buffer, corrupting the adjacent skb_shared_info region. Reject bufsize values smaller than 16; this is large enough to hold at least one KISS header byte plus useful data. Cc: stable@vger.kernel.org Cc: linux-hams@vger.kernel.org Signed-off-by: Mashiro Chen Acked-by: Joerg Reuter --- drivers/net/hamradio/scc.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/net/hamradio/scc.c b/drivers/net/hamradio/scc.c index ae5048efde686a..8569db4a71401c 100644 --- a/drivers/net/hamradio/scc.c +++ b/drivers/net/hamradio/scc.c @@ -1909,6 +1909,8 @@ static int scc_net_siocdevprivate(struct net_device *= dev, if (!capable(CAP_SYS_RAWIO)) return -EPERM; if (!arg || copy_from_user(&memcfg, arg, sizeof(memcfg))) return -EINVAL; + if (memcfg.bufsize < 16) + return -EINVAL; scc->stat.bufsize =3D memcfg.bufsize; return 0; =09 --=20 2.53.0