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mac80211: Fix rate_idx underflow in mwl8k (FS#2218)

Add a patch for mwl8k which fixes endless reboot loops on Linksys EA4500
with certain 5G configurations.

Signed-off-by: Petr Štetiar <ynezz@true.cz>
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ynezz committed Apr 8, 2019
1 parent 9e0fb5a commit 8293e7532f55f80fed0a7c729258dab116daa140
@@ -11,7 +11,7 @@ include $(INCLUDE_DIR)/kernel.mk
PKG_NAME:=mac80211

PKG_VERSION:=4.19.32-1
PKG_RELEASE:=1
PKG_RELEASE:=2
PKG_SOURCE_URL:=@KERNEL/linux/kernel/projects/backports/stable/v4.19.32/
PKG_HASH:=838db1565b54fe4bd1e769c54f30c65c9ea2fb5e99a0cddb7910561794ae317a

@@ -0,0 +1,80 @@
From b897577af85bb5e5638efa780bc3716fae5212d3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Petr=20=C5=A0tetiar?= <ynezz@true.cz>
Date: Mon, 8 Apr 2019 09:45:56 +0200
Subject: [PATCH] mwl8k: Fix rate_idx underflow
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

It was reported on OpenWrt bug tracking system[1], that several users
are affected by the endless reboot of their routers if they configure
5GHz interface with channel 44 or 48.

The reboot loop is caused by the following excessive number of WARN_ON
messages:

WARNING: CPU: 0 PID: 0 at backports-4.19.23-1/net/mac80211/rx.c:4516
ieee80211_rx_napi+0x1fc/0xa54 [mac80211]

as the messages are being correctly emitted by the following guard:

case RX_ENC_LEGACY:
if (WARN_ON(status->rate_idx >= sband->n_bitrates))

as the rate_idx is in this case erroneously set to 251 (0xfb). This fix
simply converts previously used magic number to proper constant and
guards against substraction which is leading to the currently observed
underflow.

1. https://bugs.openwrt.org/index.php?do=details&task_id=2218

Fixes: 854783444bab ("mwl8k: properly set receive status rate index on 5 GHz receive")
Cc: <stable@vger.kernel.org>
Tested-by: Eubert Bao <bunnier@gmail.com>
Reported-by: Eubert Bao <bunnier@gmail.com>
Signed-off-by: Petr Štetiar <ynezz@true.cz>
---
drivers/net/wireless/marvell/mwl8k.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/marvell/mwl8k.c b/drivers/net/wireless/marvell/mwl8k.c
index 8e4e9b6..ffc565a 100644
--- a/drivers/net/wireless/marvell/mwl8k.c
+++ b/drivers/net/wireless/marvell/mwl8k.c
@@ -441,6 +441,9 @@ struct mwl8k_sta {
#define MWL8K_CMD_UPDATE_STADB 0x1123
#define MWL8K_CMD_BASTREAM 0x1125

+#define MWL8K_LEGACY_5G_RATE_OFFSET \
+ (ARRAY_SIZE(mwl8k_rates_24) - ARRAY_SIZE(mwl8k_rates_50))
+
static const char *mwl8k_cmd_name(__le16 cmd, char *buf, int bufsize)
{
u16 command = le16_to_cpu(cmd);
@@ -1016,8 +1019,9 @@ static void mwl8k_rxd_ap_refill(void *_rxd, dma_addr_t addr, int len)

if (rxd->channel > 14) {
status->band = NL80211_BAND_5GHZ;
- if (!(status->encoding == RX_ENC_HT))
- status->rate_idx -= 5;
+ if (!(status->encoding == RX_ENC_HT) &&
+ status->rate_idx >= MWL8K_LEGACY_5G_RATE_OFFSET)
+ status->rate_idx -= MWL8K_LEGACY_5G_RATE_OFFSET;
} else {
status->band = NL80211_BAND_2GHZ;
}
@@ -1124,8 +1128,9 @@ static void mwl8k_rxd_sta_refill(void *_rxd, dma_addr_t addr, int len)

if (rxd->channel > 14) {
status->band = NL80211_BAND_5GHZ;
- if (!(status->encoding == RX_ENC_HT))
- status->rate_idx -= 5;
+ if (!(status->encoding == RX_ENC_HT) &&
+ status->rate_idx >= MWL8K_LEGACY_5G_RATE_OFFSET)
+ status->rate_idx -= MWL8K_LEGACY_5G_RATE_OFFSET;
} else {
status->band = NL80211_BAND_2GHZ;
}
--
1.9.1

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