From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx1.white.stw.pengutronix.de (mx1.white.stw.pengutronix.de [185.203.200.13]) (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 2E0B84E1C78; Fri, 9 Oct 2026 13:43:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=185.203.200.13 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791553420; cv=pass; b=hStdXFd9MTuAPPD0BerXoR6kIbjzuoo+xEFyTEjty63kj3C5UYtaBxFA9uKyNjzBnlww8CoL+nw3LzIHj7IRfqNFCSwP9v1VL3OAMaosZ7DRdqbgnnRu7kgeiL4RtO6Y3H4FG7H4JzlhtOVVscqZoCav4zMpJSM+z6QIeNq7qX4= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791553420; c=relaxed/simple; bh=g2FMKl/lBmFvFo3Km5VSg4ir60Zngr53bIY6J485DyA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BoOn5jC6c3v0fdGlqV2n7GUZb5tCA8ik0WqlWP/YsQ48ML8DdCVFRDH8otQkYMik6ZbP4t7IcqnCF3DfIiy95fQUDy5f2LaU/lH73AqRN+AyaOmXIfhzNCQCfMZau0WipkzV4xNyvE8MrT6oJ8FicSVPbRmg9jUxhtnvEytB9W8= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=pengutronix.de; spf=pass smtp.mailfrom=pengutronix.de; dkim=pass (2048-bit key) header.d=pengutronix.de header.i=@pengutronix.de header.b=dPnURIzC; arc=pass smtp.client-ip=185.203.200.13 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=pengutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=pengutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=pengutronix.de header.i=@pengutronix.de header.b="dPnURIzC" Received: from drehscheibe.grey.stw.pengutronix.de (drehscheibe.grey.stw.pengutronix.de [IPv6:2a0a:edc0:0:c01:1d::a2]) (Authenticated sender: relay-from-drehscheibe.grey.stw.pengutronix.de) by mx1.white.stw.pengutronix.de (Postfix) with ESMTPSA id A4848202626; Fri, 09 Oct 2026 15:43:35 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=pengutronix.de; s=20260414; t=1791553415; 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=Rd5lSezKIyW/9dcGa/xeP6YPWeM5EbHyXW3FSFeJnHo=; b=dPnURIzCBvv2dqfOSeHzOCyWFArVzaHgGbmdxa/WDDvp2g872SEMOcl31FrdlUgsFHfjmk Fa+AJEiF0sd55yj7kgAFpY9IDpYAQre+auv0PjuSLqxW1jYZC9fcEjuIuetBpxFfO+V9wU vwIOZG3gSYO6S3xNXMJ+t2aGFY6J1qmRkr4Ye0r1wnGIjC1Guq8f7DA6OpV2iosVV9CTA/ rCJC8lF29Rox3QhDBdTEjW28snd69b3kyO3O4kzy7O1lFn0x7nePgW4FwNzoupXBjPVTXG hdcNCI6BMbHUlprUkSQSBzBAjL5fxl02bQxfJ9mfv7avDFQXMBG1fJJDgrnMzQ== ARC-Seal: i=1; s=20260414; d=pengutronix.de; t=1791553415; a=rsa-sha256; cv=none; b=ClUao7EJZtQLCU78JsC6+ePoci60R53cnbnEmZWt8ytaeeAtL+r2zlXYjGv3qf8gUh5Nji AC+5P6qcUigZ0mmSF/Fxr8sHIvmmydOL+trPdRczgFq4l1iITXBKvWSRhrKIVqZrlocYye GZ07LaD5HCW/lE3Ll1YI9dPjSc3x0J+7ukTbkeVUX0516fF10Y3JG2d8KwxeVdfin0PLn4 rPEIDcGqCnjHOHocV4sk3h/6kNRHPwt79phI7Lvn/6j1nWNfaCH+B7jtggyBdC7Hs1+i14 lPLFbouju9TAgudJ8ojQN22ow8PIaTv4by5wHvaM/fUUMyerre715U+RhD2Jew== ARC-Authentication-Results: i=1; ORIGINATING; auth=pass smtp.auth=relay-from-drehscheibe.grey.stw.pengutronix.de smtp.mailfrom=mkl@pengutronix.de ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=pengutronix.de; s=20260414; t=1791553415; 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=Rd5lSezKIyW/9dcGa/xeP6YPWeM5EbHyXW3FSFeJnHo=; b=T6SusiKYTVr1+mBg3tmVc2cy6X6earNWFrZHNv4/X7ggrpoveTPxoEC+9RO6sRydq3W3hY IzCVhM7k5ZrVzTqeXq/8TkACXEoq8lV2NTrzjp1cn8CKbwfwHdjxYu/ofUxfaO72lrRmqV bMDlwzSbTUl70zg6DeLBgJ5CgT+OmhvRwZZ7j7Z06vkNlMa5inTqDAFPU69wEM6JKMuL9O wjJtd9h1Qrrtj8cE1omwq1t9HTluzw6fCD4UFQIkXzo0Rlzjj62KyPqd2V98iksCLNllv9 wlelUUhzEVI+9bskKb4hZS3calGbVrmLDd51RjIknlJcczQb5QAqwldeJM+XwQ== Received: from moin.white.stw.pengutronix.de ([2a0a:edc0:0:b01:1d::7b] helo=bjornoya.blackshift.org) by drehscheibe.grey.stw.pengutronix.de with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1xFAsp-0053SO-1q; Fri, 09 Oct 2026 15:43:35 +0200 Received: from blackshift.org (90-182-211-1.rcp.o2.cz [90.182.211.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519MLKEM768 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) (Authenticated sender: mkl-all@blackshift.org) by smtp.blackshift.org (Postfix) with ESMTPSA id 2971D5BD8B9; Fri, 09 Oct 2026 13:43:35 +0000 (UTC) From: Marc Kleine-Budde To: netdev@vger.kernel.org Cc: davem@davemloft.net, kuba@kernel.org, linux-can@vger.kernel.org, kernel@pengutronix.de, Cunhao Lu <1579567540@qq.com>, stable@vger.kernel.org, Vincent Mailhol , Marc Kleine-Budde Subject: [PATCH net-next 14/37] can: dev: can_put_echo_skb(): free skb on invalid echo index Date: Fri, 9 Oct 2026 15:27:46 +0200 Message-ID: <20261009134323.64064-15-mkl@pengutronix.de> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261009134323.64064-1-mkl@pengutronix.de> References: <20261009134323.64064-1-mkl@pengutronix.de> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Cunhao Lu <1579567540@qq.com> can_put_echo_skb() consumes the skb on all paths except when the echo index is out of bounds. This leaves ownership with the caller on -EINVAL, unlike the other error paths, and can leak the skb if the caller expects consistent semantics. Free the skb before returning -EINVAL so that all return paths consume it. Fixes: 6411959c10fe ("can: dev: can_put_echo_skb(): don't crash kernel if can_priv::echo_skb is accessed out of bounds") Cc: stable@vger.kernel.org Reviewed-by: Vincent Mailhol Signed-off-by: Cunhao Lu <1579567540@qq.com> Link: https://patch.msgid.link/tencent_683AA16E643DE00211CD2FB62991264DC605@qq.com Signed-off-by: Marc Kleine-Budde --- FAQ: Q: `can_skb_init_valid()` directly modifies `skb->data` without checking if the SKB is cloned or shared. Is this violating SKB shared buffer rules and causing data corruption? A: The finding about can_skb_init_valid() modifying skb->data on a potentially shared buffer is not relevant for this (correct) patch. The FDF-flag write in can_skb_init_valid() only matters for PF_PACKET use: PF_CAN allocators already set CANFD_FDF. The write exists to normalize frames for PF_PACKET observers (tcpdump/Wireshark) so they can distinguish classic CAN from CAN FD at the netdev level, and to compensate for PF_PACKET senders that omit the bit. That normalization is functionally required. The shared-buffer concern only becomes realistic through a specific chain: a PF_PACKET sender injects a CANFD-sized frame, the CAN driver's loopback puts an echo skb back into can_rcv(), and cgw (without modfuncs) clones it for forwarding to another interface. Only on that second can_skb_init_valid() call is the skb cloned. By then the bit was already set on the exclusive skb during the initial xmit path, so the flags |= CANFD_FDF write is strictly idempotent for any parallel consumer of the shared buffer - no memory-safety or information-disclosure consequence. It's a formal violation of the skb sharing rules without an observable effect, so the current code can stay as-is. Link: https://lore.kernel.org/all/54a3cc01-abcf-4a33-b932-39bb1f68cdd5@hartkopp.net/ [mkl: convert Oliver's mail to FAQ section] --- drivers/net/can/dev/skb.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/net/can/dev/skb.c b/drivers/net/can/dev/skb.c index 3e36c0368bae..738d5968dfa6 100644 --- a/drivers/net/can/dev/skb.c +++ b/drivers/net/can/dev/skb.c @@ -55,6 +55,7 @@ int can_put_echo_skb(struct sk_buff *skb, struct net_device *dev, if (idx >= priv->echo_skb_max) { netdev_err(dev, "%s: BUG! Trying to access can_priv::echo_skb out of bounds (%u/max %u)\n", __func__, idx, priv->echo_skb_max); + dev_kfree_skb_any(skb); return -EINVAL; } -- 2.53.0