From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 5B023515980; Wed, 30 Sep 2026 15:35:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790782568; cv=none; b=IqF0oVnGyIQQw0sgvzwFYyE3mlF3AxcxpW+5sFVYHxuHUpS87HANubvLI5ZNzhg+fEVEsdMrLWub+ql1yivRQgOrBPySIoRro0Xrvcq8TR38Pe0GXK4e6jPVrE6yUa9Id7VaDEbOutSrgWzLhgFK9eIjqtPoLcjgzMNyzmGH1xk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790782568; c=relaxed/simple; bh=7hNopRKrO7mFXrpRop18n3y5fg5BHWtecAH488gWrdE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=iI+2anIeYxlOSZgZ99IMzWZ34aLjcCUw5nHnsQRJTBYrxoFwH9o1E5E9d73H/LL7QGEr751sdFb3G/MvsRfm7V9ZnW1CxbXZAVwbpZOEZVQ5RqBxAega3BRGOV2EkcCA3Kz/jI+vs+vetw7nf9sVFyJAUxdCA79HFjYOx+ORLL8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=EEIML5Wn; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="EEIML5Wn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1FD691F00899; Wed, 30 Sep 2026 15:35:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790782558; bh=OGmJFZoxXUfb1LgTVtEs7OVezuxrKCWNgZX/HRAKRHI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=EEIML5WnF2VfDch3ZQ628hQk4Z0trXQepAKZCnzQaArL6yFwkzLardsvKErQPMzDE Kdp+JkA3cbag/jCoYGfIR3BO9h1/cNXZf7ftxRMxbVUsPzriE/5wGP98ecAUi3WBKp N2zmnRTKF0SUl33AgInSf032GST567skznfq2CjE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Rosen Penev , Paolo Abeni , Sasha Levin Subject: [PATCH 5.10 089/595] net: ibm: emac: Reserve VLAN header in MJS limit Date: Wed, 30 Sep 2026 17:19:42 +0200 Message-ID: <20260930152349.653522315@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152347.700140858@linuxfoundation.org> References: <20260930152347.700140858@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 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Rosen Penev [ Upstream commit 0906c117f81c2ae6e6dbfa82719f79c75e1c9325 ] The IBM EMAC programs its Maximum Jumbo Size (MJS) drop threshold from ndev->mtu directly. The hardware sizes the threshold against the L2 frame minus the ethernet header, but does not discount the 802.1Q tag, so a frame carrying a VLAN tag and a full 1500-byte payload exceeds MJS by exactly 4 bytes and is dropped. This is normally hidden because JPSM (and therefore the MJS check) only engages when the MTU is raised above ETH_DATA_LEN. With the qca8k DSA tagger the conduit MTU is bumped by QCA_HDR_LEN to 1502 during dsa_conduit_setup(), which is enough to enable JPSM and expose the off-by-VLAN-tag in the limit. Pad MJS by VLAN_HLEN so a VLAN-tagged full-MTU frame passes. Reported on Meraki MX60 (qca8k switch): tagged VLAN traffic drops at 1500-byte payload, while 1496 bytes works and untagged 1500 bytes works. Assisted-by: Claude:Opus-4.7 Signed-off-by: Rosen Penev Link: https://patch.msgid.link/20260526202247.13823-1-rosenp@gmail.com Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin --- drivers/net/ethernet/ibm/emac/core.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/net/ethernet/ibm/emac/core.c b/drivers/net/ethernet/ibm/emac/core.c index c00b9097eeea4..61cc137c54f8a 100644 --- a/drivers/net/ethernet/ibm/emac/core.c +++ b/drivers/net/ethernet/ibm/emac/core.c @@ -30,6 +30,7 @@ #include #include #include +#include #include #include #include @@ -464,7 +465,7 @@ static inline u32 emac_iff2rmr(struct net_device *ndev) if (emac_has_feature(dev, EMAC_APM821XX_REQ_JUMBO_FRAME_SIZE)) { r &= ~EMAC4_RMR_MJS_MASK; - r |= EMAC4_RMR_MJS(ndev->mtu); + r |= EMAC4_RMR_MJS(ndev->mtu + VLAN_HLEN); } return r; -- 2.53.0