From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753622AbaLFPUe (ORCPT ); Sat, 6 Dec 2014 10:20:34 -0500 Received: from ip4-83-240-67-251.cust.nbox.cz ([83.240.67.251]:47711 "EHLO ip4-83-240-18-248.cust.nbox.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752083AbaLFPIF (ORCPT ); Sat, 6 Dec 2014 10:08:05 -0500 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Stanislaw Gruszka , "John W. Linville" , Jiri Slaby Subject: [PATCH 3.12 57/66] rt2x00: do not align payload on modern H/W Date: Sat, 6 Dec 2014 16:07:49 +0100 Message-Id: <8c3b78ffdeff62372503e92c606a262be51fb19a.1417878427.git.jslaby@suse.cz> X-Mailer: git-send-email 2.1.3 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Stanislaw Gruszka 3.12-stable review patch. If anyone has any objections, please let me know. =============== 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: Jiri Slaby --- drivers/net/wireless/rt2x00/rt2x00queue.c | 50 ++++++++----------------------- 1 file changed, 12 insertions(+), 38 deletions(-) diff --git a/drivers/net/wireless/rt2x00/rt2x00queue.c b/drivers/net/wireless/rt2x00/rt2x00queue.c index 66a2db8c260d..e6182170e791 100644 --- a/drivers/net/wireless/rt2x00/rt2x00queue.c +++ b/drivers/net/wireless/rt2x00/rt2x00queue.c @@ -160,55 +160,29 @@ void rt2x00queue_align_frame(struct sk_buff *skb) 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; + unsigned int l2pad = (skb->len > hdr_len) ? L2PAD_SIZE(hdr_len) : 0; - /* - * Adjust the header alignment if the payload needs to be moved more - * than the header. - */ - if (payload_align > header_align) - header_align += 4; - - /* 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); } -- 2.1.3