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=1794591178; b=SEXWjR/ED5P5TGymAUACCFivwRice/jV89u85VKDLPgoLUtX/iQ1A6ve1u1N2S786CiZ p2+mKkqABdAaxGnZBqH2uw4vBfIjZq0YcGZ+DfAVZ9du11fIMFlYecOLvHeRxbd/lGG1A oA5zSom+v7nvMY4ZrsUr/PO0nGBDy5N5ZlqkIZKZXLbii2kRGP0K+rfU3E3IuiEHUrqNi XadIYBXiQieLBUezanz0EVF3AcGR1Pck/C9WxM1q3ZzNFr/aJReFTyrUbBFjNhHRbKxim dw3cCq/BLE61qLd7kyeOe3M9vs5dujo34TuEdpoL5hYjVLBlEtq+nL8dxEU+4Kk2riQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794591178; 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=k5oX0GoSPKzyxycvw22Gb21MaTjTYBNASXNVgo3svbY=; b=A2sKuLOoScIG6ZFutDNCCtBIzhB4yv66l8M53AZ65CjdtHrk6XA+gbRW6a6dJrKhtijq U2JSgNKjuYv+XR0PMT7am2WdCYL1ZD/yGPlz3LU4VMIbGh1PwqoeUguRGhhFl7++nyVUX jwjlYaVgo4rEDA7Blw5ooQy6ijXSOwZ1DFfftrKKcJqGWXrjWT80xPr4hAnyltefzo3OB BJ7H7w7aeOuYxkIC9iZFOG050nk8IO16puCKfoWaioKTOtCTnCGZT1w+ScXecHLRc+hLC tHyubmXFy86KXi+4hU8eWQx7phTkC5cYO2+dyi+vXoUzI+b7KavZat26AGt7llpkI5g== 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=QAyita6j; 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 468C76073FE2; Fri, 13 Nov 2026 17:32:58 +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=QAyita6j Received: by smtp.kernel.org (Postfix) with ESMTPSA id E5F5D1F000C4; Fri, 13 Nov 2026 17:32:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794591178; bh=k5oX0GoSPKzyxycvw22Gb21MaTjTYBNASXNVgo3svbY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=QAyita6jyPsBhTJVdYSDapNJQ/UQeB6b8+NKLFaYopWjM2WaVXMxCUI0jzndHZGWs Gj0peD4+blLvx1uanjr9fRCCJJU0Cd9s2pCiqk0HKhXIFmTVbxhSYzQG3Lx1fkwtYm 07GWGd8QwnKlXbp6jFGZqLZdkrtm5ag3h3NIqvKc= 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 6.12 317/670] can: dev: can_put_echo_skb(): free skb on invalid echo index Date: Fri, 13 Nov 2026 10:48:01 -0500 Message-ID: <20261113153822.640562910@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153811.177190860@linuxfoundation.org> References: <20261113153811.177190860@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-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 3ebd4f779b9bd..6fb1f9b2a9e20 100644 --- a/drivers/net/can/dev/skb.c +++ b/drivers/net/can/dev/skb.c @@ -52,6 +52,7 @@ 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