netdev - [PATCH AUTOSEL 4.4 04/16] mwifiex: set needed_headroom, not hard_header

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Date:   Sat, 11 Apr 2020 19:14:34 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Brian Norris <briannorris@...omium.org>,
        Ganapathi Bhat <ganapathi.gbhat@....com>,
        Kalle Valo <kvalo@...eaurora.org>,
        Sasha Levin <sashal@...nel.org>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 4.4 04/16] mwifiex: set needed_headroom, not hard_header_len

From: Brian Norris <briannorris@...omium.org>

[ Upstream commit 9454f7a895b822dd8fb4588fc55fda7c96728869 ]

hard_header_len provides limitations for things like AF_PACKET, such
that we don't allow transmitting packets smaller than this.

needed_headroom provides a suggested minimum headroom for SKBs, so that
we can trivally add our headers to the front.

The latter is the correct field to use in this case, while the former
mostly just prevents sending small AF_PACKET frames.

In any case, mwifiex already does its own bounce buffering [1] if we
don't have enough headroom, so hints (not hard limits) are all that are
needed.

This is the essentially the same bug (and fix) that brcmfmac had, fixed
in commit cb39288fd6bb ("brcmfmac: use ndev->needed_headroom to reserve
additional header space").

[1] mwifiex_hard_start_xmit():
	if (skb_headroom(skb) < MWIFIEX_MIN_DATA_HEADER_LEN) {
	[...]
		/* Insufficient skb headroom - allocate a new skb */

Fixes: 5e6e3a92b9a4 ("wireless: mwifiex: initial commit for Marvell mwifiex driver")
Signed-off-by: Brian Norris <briannorris@...omium.org>
Acked-by: Ganapathi Bhat <ganapathi.gbhat@....com>
Signed-off-by: Kalle Valo <kvalo@...eaurora.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/wireless/mwifiex/cfg80211.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/mwifiex/cfg80211.c b/drivers/net/wireless/mwifiex/cfg80211.c
index c6c2d3304dba7..4f4af48fc3fc6 100644
--- a/drivers/net/wireless/mwifiex/cfg80211.c
+++ b/drivers/net/wireless/mwifiex/cfg80211.c
@@ -2755,7 +2755,7 @@ struct wireless_dev *mwifiex_add_virtual_intf(struct wiphy *wiphy,
 
 	dev->flags |= IFF_BROADCAST | IFF_MULTICAST;
 	dev->watchdog_timeo = MWIFIEX_DEFAULT_WATCHDOG_TIMEOUT;
-	dev->hard_header_len += MWIFIEX_MIN_DATA_HEADER_LEN;
+	dev->needed_headroom = MWIFIEX_MIN_DATA_HEADER_LEN;
 	dev->ethtool_ops = &mwifiex_ethtool_ops;
 
 	mdev_priv = netdev_priv(dev);
-- 
2.20.1