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 61E371F16B; Sat, 17 Oct 2026 17:09:45 +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=1792256986; cv=none; b=L4VmHiOZrtwTakjZli4/u9UYwVhncj/QixDBFd+Uo+KUhbFdSkuM3Yng/3Xx1bF8USIMVOZlE3a9YMnlZSBx5kg6ZTm26POihUP7MFFsAfIO9xSml3izEBAF3qOw7tL5SCrDhGFo0tQMUHNtoGizrjMEOE/2rT5OBkb92eEl4IM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792256986; c=relaxed/simple; bh=Kqy/SU+DplbC/vs5XgXoNI5XDwY/4clq70sBm6UGS+A=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=UuJpMIuMupaLwGaMACAV18dxI9bZ1zRYkC0vKD8OdyAVFuFnwkNJONLC0TEv2Ufvy3VtiiRqLQutRQYflHo4wz7znMn4ZSIg0CpPZrO3Kxsc05Nb8ErZctyfXflgaVRs7EmCUZFRVdRue6vjuMHFHQqvhdtKTMeyvhG61JCxinY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=XolUsEN8; 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="XolUsEN8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AE1151F000C4; Sat, 17 Oct 2026 17:09:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792256985; bh=oqJs1q3bikNr4GPzSGSkvoP+vlRLbhDHJ/QXpxIsWoE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=XolUsEN8YbyIlXyh4d7D9prv59DRxpO9ivRryeLHu2vzvM2q0t1wMOPUm1QHCbV2H Wp3YDG5W8YmJyoJFfhGFot2oLblsous1Z1a6ND83yi3R8T3qRJjUbH1QnQkIKllQvM rp9pDwUG9VLJgEqYzlhapymkP6Zkv/nBWvimizUw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Stefan Fleischmann , Eric Dumazet , Michael Chan , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.6 0415/1674] bnxt_en: fix DMA mapping length for padded small packets Date: Sat, 17 Oct 2026 17:44:47 +0200 Message-ID: <20261017160441.780771426@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261017160431.119607952@linuxfoundation.org> References: <20261017160431.119607952@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 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit a51d233ccd4889aadb71dace863525cc2b00271e ] Stefan Fleischmann reported Intel IOMMU DMA Read faults on BCM57412 NetXtreme-E NICs when transmitting packets on VLAN/macvlan interfaces: DMAR: [DMA Read NO_PASID] Request device [18:00.0] fault addr 0xfc499000 [fault reason 0x06] PTE Read access is not set bnxt_en 0000:18:00.0 eno1np0: Abandoning msg {0xb4 0x41a} len: 0 due to firmware status: 0x2000001 ... NETDEV WATCHDOG: eno1np0 (bnxt_en): transmit queue 0 timed out The fault address (0xfc499000) is on an exact 4KB page boundary, pointing to a DMA read buffer overrun. In bnxt_start_xmit(), packets smaller than BNXT_MIN_PKT_SIZE (52 bytes), such as 42-byte untagged ARP frames, are padded: if (length < BNXT_MIN_PKT_SIZE) { pad = BNXT_MIN_PKT_SIZE - length; if (skb_pad(skb, pad)) goto tx_kick_pending; length = BNXT_MIN_PKT_SIZE; } mapping = dma_map_single(&pdev->dev, skb->data, len, DMA_TO_DEVICE); ... dma_unmap_len_set(tx_buf, len, len); However, 'len' was initialized earlier to skb_headlen(skb) (e.g. 42 bytes) and is left unadjusted after padding. Consequently, dma_map_single() and dma_unmap_len_set() map and track only 42 bytes. Later, the hardware TX buffer descriptor is programmed with the padded length: txbd->tx_bd_len_flags_type = cpu_to_le32(((len + pad) << TX_BD_LEN_SHIFT) | flags | TX_BD_FLAGS_PACKET_END); The NIC DMA engine is thus instructed to read 52 bytes from a region where only 42 bytes were DMA-mapped. If skb->data ends near the boundary of a 4KB page (within 'pad' bytes of the next page), the hardware DMA read overruns into the unmapped adjacent page, triggering an IOMMU fault. This issue was exposed after commit 447cbe95ebb9 ("vlan: fix skb_under_panic and races when toggling HW VLAN offload") because reserving extra VLAN headroom rounded LL_RESERVED_SPACE from 48 up to 64 bytes, shifting skb->data offsets and potentially causing small frames to land right against page boundaries. Fix this by using skb_put_padto(skb, BNXT_MIN_PKT_SIZE) in bnxt_start_xmit(), before skb_shinfo(skb)->nr_frags is sampled, because padding might linearize the skb. This ensures skb->len and skb_headlen(skb) reflect the padded size so that dma_map_single() maps the full buffer and the descriptor length is consistent. This also removes the temporary 'pad' variable and masking logic. The padding is done after the SW USO branch, otherwise bnxt_sw_udp_gso_xmit() would account the padding as UDP payload and send it in extra segments. Note that SW USO segments are still not padded: with IPv4, a segment carrying less than 10 bytes of UDP payload (small gso_size, or a short last segment) is sent as a frame shorter than BNXT_MIN_PKT_SIZE. This is a separate issue, left for a followup patch. Fixes: c0c050c58d84 ("bnxt_en: New Broadcom ethernet driver.") Cc: stable@vger.kernel.org Reported-by: Stefan Fleischmann Closes: https://lore.kernel.org/netdev/20261004122616.56714cbd@nargothrond/ Signed-off-by: Eric Dumazet Reviewed-by: Michael Chan Link: https://patch.msgid.link/20261007051747.455273-1-edumazet@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- drivers/net/ethernet/broadcom/bnxt/bnxt.c | 23 ++++++++++------------- 1 file changed, 10 insertions(+), 13 deletions(-) diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c index 0e1a88a0df3d5..304170ceba7f2 100644 --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c @@ -394,7 +394,7 @@ static netdev_tx_t bnxt_start_xmit(struct sk_buff *skb, struct net_device *dev) struct netdev_queue *txq; int i; dma_addr_t mapping; - unsigned int length, pad = 0; + unsigned int length; u32 len, free_size, vlan_tag_flags, cfa_action, flags; u16 prod, last_frag; struct pci_dev *pdev = bp->pdev; @@ -413,6 +413,14 @@ static netdev_tx_t bnxt_start_xmit(struct sk_buff *skb, struct net_device *dev) txr = &bp->tx_ring[bp->tx_ring_map[i]]; prod = txr->tx_prod; + /* Must be done before skb_shinfo(skb)->nr_frags is sampled, + * because skb_put_padto() might linearize the skb. + */ + if (skb_put_padto(skb, BNXT_MIN_PKT_SIZE)) { + /* SKB already freed. */ + goto tx_kick_pending; + } + free_size = bnxt_tx_avail(bp, txr); if (unlikely(free_size < skb_shinfo(skb)->nr_frags + 2)) { /* We must have raced with NAPI cleanup */ @@ -545,14 +553,6 @@ static netdev_tx_t bnxt_start_xmit(struct sk_buff *skb, struct net_device *dev) } normal_tx: - if (length < BNXT_MIN_PKT_SIZE) { - pad = BNXT_MIN_PKT_SIZE - length; - if (skb_pad(skb, pad)) - /* SKB already freed. */ - goto tx_kick_pending; - length = BNXT_MIN_PKT_SIZE; - } - mapping = dma_map_single(&pdev->dev, skb->data, len, DMA_TO_DEVICE); if (unlikely(dma_mapping_error(&pdev->dev, mapping))) @@ -624,10 +624,7 @@ static netdev_tx_t bnxt_start_xmit(struct sk_buff *skb, struct net_device *dev) txbd->tx_bd_len_flags_type = cpu_to_le32(flags); } - flags &= ~TX_BD_LEN; - txbd->tx_bd_len_flags_type = - cpu_to_le32(((len + pad) << TX_BD_LEN_SHIFT) | flags | - TX_BD_FLAGS_PACKET_END); + txbd->tx_bd_len_flags_type |= cpu_to_le32(TX_BD_FLAGS_PACKET_END); netdev_tx_sent_queue(txq, skb->len); -- 2.53.0