From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794585681; b=LkPgzdgpVUtkhd6FGPEVKmlJ+WfVLA22j4ESaTlonT30pgWXJZ72ZJTqT1THgN7zm49F S6e76WdLmwNVaHsdTcvFSVzbadQ+8zF1B71UKrhhwU9biX8TwKqGUN0I1on4a+bK0jJxv jc9f9ZbWocHwTTFwNoMIA25ePVHS9OBY41lpNoCwX9S6BF3tfMSay0GSy5ATTMqpoCUF8 KGhJRx4sD9TNwnkNFKLmTg17FxtjiGOIWep4wHNlIBnQszMC/6T1aFXpTCNn8QIv6w30p GccpbgwKTQuNxmaemu17aesUvstwIs9IYcgmeO95/oS5wk4fYmOtDEyg8ELhaHcB7wQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794585681; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=r8GK3maxeJ2Cca66Mf050FEBp7FUEgXd2b/rBQJs0e4=; b=RvgK3L/5gWAuM1SgNhwha+dkOG9IoSdzKIJeeC3Ik06vA+b/or/uXPqRJtL9nq0FullG J2GJ6XksCdMCFndCxNvcRv4TbF8M24aLof4rhRzSwLjt/cbliJhjof36M8/afHFEMWWZl cIuXKK3HydMYKumtB2d6cBj3h5AOYVWaEsPus9DpW7V1PPckGDcMNYq1/a8ab5b1kX5mN O3lRn1RSv39lXRwuYw8no2fmR4joZKLBetzIQmbMSb2P2HQsE2/GcpJWpzTxHy4oJwJ3L 9iTOkmHu2Hiywe3Sy6PD3LKSmIrtenELsVy1GLIoWFGWy/RY8vLRPhBVkAfBu0EqntA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=cYXbJgYr; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A5450606A335; Fri, 13 Nov 2026 16:01:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=cYXbJgYr Received: by smtp.kernel.org (Postfix) with ESMTPSA id 502221F000C4; Fri, 13 Nov 2026 16:01:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794585681; bh=r8GK3maxeJ2Cca66Mf050FEBp7FUEgXd2b/rBQJs0e4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=cYXbJgYrtF/95MrP4wLVGJvFbW+UToI8MfyjvgP7HsHGIezfesLM/gX16CQ4fkqjf 6yfwkSmihlY0UgbkSxAOAW4hlK3PA064655p1PoNzTrz/zt65fm0Z0e3E8FfzpqQcs 1Lu71es7OAeGQdGkyRjDhJ1W/0sxbi9RXXgFjleE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Vincent Mailhol , Cunhao Lu <1579567540@qq.com>, Marc Kleine-Budde , Sasha Levin Subject: [PATCH 7.3 293/507] can: dev: can_put_echo_skb(): free skb on invalid echo index Date: Fri, 13 Nov 2026 10:49:57 -0500 Message-ID: <20261113153805.180900955@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153753.358973689@linuxfoundation.org> References: <20261113153753.358973689@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: Cunhao Lu <1579567540@qq.com> [ Upstream commit b4ebcbbf66ba6c5816dfe229effb4641c46e4b4c ] 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] Signed-off-by: Sasha Levin --- 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 46c151eece8f7..9e274147ffe56 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