Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760826AbaLLGhr (ORCPT ); Fri, 12 Dec 2014 01:37:47 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:51846 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759039AbaLLGQ4 (ORCPT ); Fri, 12 Dec 2014 01:16:56 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Stanislaw Gruszka" , "Henrik Asp" , "John W. Linville" Date: Fri, 12 Dec 2014 06:14:25 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 125/164] rt2x00: do not align payload on modern H/W In-Reply-To: X-SA-Exim-Connect-IP: 2001:470:1f08:1539:c97:8151:cc89:c28d X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.65-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Stanislaw Gruszka commit cfd9167af14eb4ec21517a32911d460083ee3d59 upstream. RT2800 and newer hardware require padding between header and payload if header length is not multiple of 4. For historical reasons we also align payload to to 4 bytes boundary, but such alignment is not needed on modern H/W. Patch fixes skb_under_panic problems reported from time to time: https://bugzilla.kernel.org/show_bug.cgi?id=84911 https://bugzilla.kernel.org/show_bug.cgi?id=72471 http://marc.info/?l=linux-wireless&m=139108549530402&w=2 https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1087591 Panic happened because we eat 4 bytes of skb headroom on each (re)transmission when sending frame without the payload and the header length not being multiple of 4 (i.e. QoS header has 26 bytes). On such case because paylad_aling=2 is bigger than header_align=0 we increase header_align by 4 bytes. To prevent that we could change the check to: if (payload_length && payload_align > header_align) header_align += 4; but not aligning payload at all is more effective and alignment is not really needed by H/W (that has been tested on OpenWrt project for few years now). Reported-and-tested-by: Antti S. Lankila Debugged-by: Antti S. Lankila Reported-by: Henrik Asp Originally-From: Helmut Schaa Signed-off-by: Stanislaw Gruszka Signed-off-by: John W. Linville Signed-off-by: Ben Hutchings --- drivers/net/wireless/rt2x00/rt2x00queue.c | 50 ++++++++----------------------- 1 file changed, 12 insertions(+), 38 deletions(-) --- a/drivers/net/wireless/rt2x00/rt2x00queue.c +++ b/drivers/net/wireless/rt2x00/rt2x00queue.c @@ -148,55 +148,29 @@ void rt2x00queue_align_frame(struct sk_b skb_trim(skb, frame_length); } -void rt2x00queue_insert_l2pad(struct sk_buff *skb, unsigned int header_length) +/* + * H/W needs L2 padding between the header and the paylod if header size + * is not 4 bytes aligned. + */ +void rt2x00queue_insert_l2pad(struct sk_buff *skb, unsigned int hdr_len) { - unsigned int payload_length = skb->len - header_length; - unsigned int header_align = ALIGN_SIZE(skb, 0); - unsigned int payload_align = ALIGN_SIZE(skb, header_length); - unsigned int l2pad = payload_length ? L2PAD_SIZE(header_length) : 0; - - /* - * Adjust the header alignment if the payload needs to be moved more - * than the header. - */ - if (payload_align > header_align) - header_align += 4; + unsigned int l2pad = (skb->len > hdr_len) ? L2PAD_SIZE(hdr_len) : 0; - /* There is nothing to do if no alignment is needed */ - if (!header_align) + if (!l2pad) return; - /* Reserve the amount of space needed in front of the frame */ - skb_push(skb, header_align); - - /* - * Move the header. - */ - memmove(skb->data, skb->data + header_align, header_length); - - /* Move the payload, if present and if required */ - if (payload_length && payload_align) - memmove(skb->data + header_length + l2pad, - skb->data + header_length + l2pad + payload_align, - payload_length); - - /* Trim the skb to the correct size */ - skb_trim(skb, header_length + l2pad + payload_length); + skb_push(skb, l2pad); + memmove(skb->data, skb->data + l2pad, hdr_len); } -void rt2x00queue_remove_l2pad(struct sk_buff *skb, unsigned int header_length) +void rt2x00queue_remove_l2pad(struct sk_buff *skb, unsigned int hdr_len) { - /* - * L2 padding is only present if the skb contains more than just the - * IEEE 802.11 header. - */ - unsigned int l2pad = (skb->len > header_length) ? - L2PAD_SIZE(header_length) : 0; + unsigned int l2pad = (skb->len > hdr_len) ? L2PAD_SIZE(hdr_len) : 0; if (!l2pad) return; - memmove(skb->data + l2pad, skb->data, header_length); + memmove(skb->data + l2pad, skb->data, hdr_len); skb_pull(skb, l2pad); } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/