From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 CA96530505F; Tue, 30 Sep 2025 14:53:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759244021; cv=none; b=Kgb/pgPxJN4x2h+KD6AiJ/tDgfMHLIUv/bbIKNM+crC1B7SC505fpFex4+VU+OqBxd/H3XZ3EK/xji0nfrpyH4BiuKp6amEyGk+9bsOHkvFjdjEtRZi5Kv2Jgm1PlY40+4B0DfJRcH2VjqC1xV4LNhX7pAf6PjnpjyhdtYpwhRg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759244021; c=relaxed/simple; bh=VQCXwephyS9v1H/D3n3Kl2YnGDHVJ7Ko0LmTZY74pY8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=XbYRYYvDG/+ylAj14DR/YX1aBdgcPzPRrYL/iwcNyvI8+ZWC4ndiuYeWLIJK5zk3g6gYJlC0iGlNFdx+f+RzkK9bHWi8o3dczncN/3lty28Xbgsaz3Y8cPe0EQEWbQZfbOWsz+AW/kAfxhWJAg6Gn1uWMna8USJ0c7YFpO+foCU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=2cLR0NPA; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="2cLR0NPA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3B69FC4CEF0; Tue, 30 Sep 2025 14:53:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1759244021; bh=VQCXwephyS9v1H/D3n3Kl2YnGDHVJ7Ko0LmTZY74pY8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=2cLR0NPAG+V5liLCv0Fa1c6z3VpTjdDOIEMUUkCDBjo61Z1WKkJ9roCTzyPZMr3NY u2I3DYTho8f1Kx1nQLZc3IzbEUR7HHdDDOvvBUsC9YQ5sUkEmEYFUTRwLjJJPJAPOm H2nWKQQ4Stp1O/6EdCiqTk1qRHCCDqD22UiUYQPM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Vincent Mailhol , Marc Kleine-Budde , Sasha Levin Subject: [PATCH 5.4 66/81] can: sun4i_can: populate ndo_change_mtu() to prevent buffer overflow Date: Tue, 30 Sep 2025 16:47:08 +0200 Message-ID: <20250930143822.446635566@linuxfoundation.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20250930143819.654157320@linuxfoundation.org> References: <20250930143819.654157320@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vincent Mailhol [ Upstream commit 61da0bd4102c459823fbe6b8b43b01fb6ace4a22 ] Sending an PF_PACKET allows to bypass the CAN framework logic and to directly reach the xmit() function of a CAN driver. The only check which is performed by the PF_PACKET framework is to make sure that skb->len fits the interface's MTU. Unfortunately, because the sun4i_can driver does not populate its net_device_ops->ndo_change_mtu(), it is possible for an attacker to configure an invalid MTU by doing, for example: $ ip link set can0 mtu 9999 After doing so, the attacker could open a PF_PACKET socket using the ETH_P_CANXL protocol: socket(PF_PACKET, SOCK_RAW, htons(ETH_P_CANXL)) to inject a malicious CAN XL frames. For example: struct canxl_frame frame = { .flags = 0xff, .len = 2048, }; The CAN drivers' xmit() function are calling can_dev_dropped_skb() to check that the skb is valid, unfortunately under above conditions, the malicious packet is able to go through can_dev_dropped_skb() checks: 1. the skb->protocol is set to ETH_P_CANXL which is valid (the function does not check the actual device capabilities). 2. the length is a valid CAN XL length. And so, sun4ican_start_xmit() receives a CAN XL frame which it is not able to correctly handle and will thus misinterpret it as a CAN frame. This can result in a buffer overflow. The driver will consume cf->len as-is with no further checks on this line: dlc = cf->len; Here, cf->len corresponds to the flags field of the CAN XL frame. In our previous example, we set canxl_frame->flags to 0xff. Because the maximum expected length is 8, a buffer overflow of 247 bytes occurs a couple line below when doing: for (i = 0; i < dlc; i++) writel(cf->data[i], priv->base + (dreg + i * 4)); Populate net_device_ops->ndo_change_mtu() to ensure that the interface's MTU can not be set to anything bigger than CAN_MTU. By fixing the root cause, this prevents the buffer overflow. Fixes: 0738eff14d81 ("can: Allwinner A10/A20 CAN Controller support - Kernel module") Signed-off-by: Vincent Mailhol Link: https://patch.msgid.link/20250918-can-fix-mtu-v1-3-0d1cada9393b@kernel.org Signed-off-by: Marc Kleine-Budde Signed-off-by: Sasha Levin --- drivers/net/can/sun4i_can.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/net/can/sun4i_can.c b/drivers/net/can/sun4i_can.c index 0eddd5779e5a2..a1e151d373597 100644 --- a/drivers/net/can/sun4i_can.c +++ b/drivers/net/can/sun4i_can.c @@ -752,6 +752,7 @@ static const struct net_device_ops sun4ican_netdev_ops = { .ndo_open = sun4ican_open, .ndo_stop = sun4ican_close, .ndo_start_xmit = sun4ican_start_xmit, + .ndo_change_mtu = can_change_mtu, }; static const struct of_device_id sun4ican_of_match[] = { -- 2.51.0