Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit cfd9167a authored by Stanislaw Gruszka's avatar Stanislaw Gruszka Committed by John W. Linville
Browse files

rt2x00: do not align payload on modern H/W 

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: default avatarAntti S. Lankila <alankila@bel.fi>
Debugged-by: default avatarAntti S. Lankila <alankila@bel.fi>
Reported-by: default avatarHenrik Asp <solenskiner@gmail.com>
Originally-From: Helmut Schaa <helmut.schaa@googlemail.com>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarStanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: default avatarJohn W. Linville <linville@tuxdriver.com>
parent 9d828ad7

drivers/net/wireless/rt2x00/rt2x00queue.c

+12 −38
Original line number Diff line number Diff line
@@ -158,55 +158,29 @@ 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)

{

	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.

 * H/W needs L2 padding between the header and the paylod if header size

 * is not 4 bytes aligned.

 */

	if (payload_align > header_align)

		header_align += 4;

void rt2x00queue_insert_l2pad(struct sk_buff *skb, unsigned int hdr_len)

{

	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);

}