From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out28-125.mail.aliyun.com (out28-125.mail.aliyun.com [115.124.28.125]) (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 4CE9039CD14; Wed, 9 Sep 2026 17:31:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.28.125 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788975082; cv=none; b=X8wuazN8rzBBUko4CPjKNE+7UNNbywWypWq8HZbfxgUIF2wT0IeIJea9ffqxbXPz1bhUPnpy+MlyEEi57tuBZIugwuFlaD+zgjsnpJyVuxbInFMOFuMQC9E9PPLQJ8NjZ7j2+36OhGujdNawx7Jy64aiPr6ta9uAneqZDseYyJ4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788975082; c=relaxed/simple; bh=fOLMYKi+nbgaU8spr87cltPjB56CXayMVROFNlqZH/o=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=qsf7IJTCT2y5mhZ2CNAkjrKe7/RV0jVFrnPHtRZCJ+Fr/XNv3ZhtXpDACvvFmJxo8rc+XiVhIfx95Y14cuqq4+IeolDfR54qx0CV42Y53DjnJVsVwbRXvYa0mjHCFPus8jP4aFs2KacQ9NAinC571ciAEIYH8HxOpl3NirLFRDs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=xiaopeng.com; spf=pass smtp.mailfrom=xiaopeng.com; dkim=pass (1024-bit key) header.d=xiaopeng.com header.i=@xiaopeng.com header.b=ptwxU3jS; arc=none smtp.client-ip=115.124.28.125 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=xiaopeng.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=xiaopeng.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=xiaopeng.com header.i=@xiaopeng.com header.b="ptwxU3jS" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=xiaopeng.com; s=default; t=1788975072; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=aOQCNzihXEftM2gN4JZ6DNSjPsRK5i/nabKuwuh9rR4=; b=ptwxU3jSs4btt9eLyxk81TB8kpTVz8u7VJ2yfUbSvh6V8IPwXb5rnmq11NR0s3rxeUJqQpxHqA2bZdmLPZ83HfCHZKZ2dJ0/V+nywCb5qhDRBzSxUz2RzS0lxoa23zROWWodYPGOWhMLjUt6YDEbOHZaJHBttDYAy/KpvuIM01Q= X-Alimail-AntiSpam:AC=CONTINUE;BC=0.07544608|-1;CH=green;DM=|CONTINUE|false|;DS=CONTINUE|ham_alarm|0.00433042-0.00078299-0.994887;FP=9821315156926840689|0|0|0|0|-1|-1|-1;HT=maildocker-contentspam033037071049;MF=liuc63@xiaopeng.com;NM=1;PH=DS;RN=10;RT=10;SR=0;TI=SMTPD_---.j9p79sU_1788975069; Received: from localhost(mailfrom:liuc63@xiaopeng.com fp:SMTPD_---.j9p79sU_1788975069 cluster:ay29) by smtp.aliyun-inc.com; Thu, 10 Sep 2026 01:31:11 +0800 From: Liu Chao To: Robin van der Gracht , Oleksij Rempel , Oliver Hartkopp , Marc Kleine-Budde Cc: kernel@pengutronix.de, linux-can@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Liu Chao Subject: [PATCH net v2 1/2] can: j1939: reject TP RTS with wrong packet count Date: Thu, 10 Sep 2026 01:31:03 +0800 Message-ID: <20260909173105.158202-2-liuc63@xiaopeng.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260909173105.158202-1-liuc63@xiaopeng.com> References: <20260909173105.158202-1-liuc63@xiaopeng.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit j1939_xtp_rx_rts_session_new() computes the expected packet count as (len + 6) / 7, then unconditionally overwrites it with dat[3] from the incoming RTS, even when the two disagree. When dat[3] is smaller, the session completes after fewer packets than the buffer was sized for, delivering a short (zero-padded) message to userspace. Neither direction of mismatch works today: a smaller dat[3] completes the session early and hands a truncated message to userspace, while a larger one makes j1939_session_skb_get_by_offset() fail once the offset runs past the buffer, aborting the session anyway. Rejecting the RTS up front does not break any transfer that currently works. Abort the session when dat[3] doesn't match, similar to how a4fbe70c5cb7 ("can: j1939: j1939_xtp_rx_rts_session_new(): abort TP less than 9 bytes") rejects out-of-range message sizes. An alternative would be to silently keep the computed value and ignore dat[3], but that doesn't actually work: the sender only transmits dat[3] packets, so the receiver would never collect enough to complete and would hang until the rx timeout fires -- a worse failure mode than a clean abort with a clear log message. # RTS: len=100 (dat[1..2]=0x0064) but dat[3]=1 (should be 15) cansend vcan0 18EC8090#1064000103002301 Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol") Cc: stable@vger.kernel.org Signed-off-by: Liu Chao --- net/can/j1939/transport.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c index 8fcfd13e5..c40db4337 100644 --- a/net/can/j1939/transport.c +++ b/net/can/j1939/transport.c @@ -1672,11 +1672,16 @@ j1939_session *j1939_xtp_rx_rts_session_new(struct j1939_priv *priv, session->pkt.total = (len + 6) / 7; session->pkt.block = 0xff; if (skcb.addr.type != J1939_ETP) { - if (dat[3] != session->pkt.total) - netdev_alert(priv->ndev, "%s: 0x%p: strange total, %u != %u\n", - __func__, session, session->pkt.total, - dat[3]); - session->pkt.total = dat[3]; + if (dat[3] != session->pkt.total) { + netdev_warn_once(priv->ndev, + "%s: 0x%p: packet count mismatch, calc %u != RTS %u, abort\n", + __func__, session, + session->pkt.total, dat[3]); + j1939_xtp_tx_abort(priv, &skcb, true, + J1939_XTP_ABORT_FAULT, pgn); + j1939_session_put(session); + return NULL; + } session->pkt.block = min(dat[3], dat[4]); } -- 2.50.1