linux-kernel - [PATCH AUTOSEL for 4.14 06/84] iwlwifi: mvm: rs: don't override the rate history in the search cycle

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Message-ID: <20180303222518.26271-6-alexander.levin@microsoft.com>
Date:   Sat, 3 Mar 2018 22:26:03 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
CC:     Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
        Luca Coelho <luciano.coelho@...el.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL for 4.14 06/84] iwlwifi: mvm: rs: don't override the
 rate history in the search cycle

From: Emmanuel Grumbach <emmanuel.grumbach@...el.com>

[ Upstream commit 992172e3aec19e5b0ea5b757ba40a146b9282d1e ]

When we are in a search cycle, we try different combinations
of parameters. Those combinations are called 'columns'.
When we switch to a new column, we first need to check if
this column has a suitable rate, if not, we can't try it.
This means we must not erase the statistics we gathered
for the previous column until we are sure that we are
indeed switching column.

The code that tries to switch to a new column first sets
a whole bunch of things for the new column, and only then
checks that we can find suitable rates in that column.
While doing that, the code mistakenly erased the rate
statistics. This code was right until
struct iwl_scale_tbl_info grew up for TPC.

Fix this to make sure we don't erase the rate statistics
until we are sure that we can indeed switch to the new
column.

Note that this bug is really harmless since it causes a
change in the behavior only when we can't find any rate
in the new column which should really not happen. In the
case we do find a suitable we reset the rate statistics
a few lines later anyway.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@...el.com>
Signed-off-by: Luca Coelho <luciano.coelho@...el.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 drivers/net/wireless/intel/iwlwifi/mvm/rs.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/rs.c b/drivers/net/wireless/intel/iwlwifi/mvm/rs.c
index 0fe723ca844e..d22cef7381ba 100644
--- a/drivers/net/wireless/intel/iwlwifi/mvm/rs.c
+++ b/drivers/net/wireless/intel/iwlwifi/mvm/rs.c
@@ -1881,12 +1881,10 @@ static int rs_switch_to_column(struct iwl_mvm *mvm,
 	struct rs_rate *rate = &search_tbl->rate;
 	const struct rs_tx_column *column = &rs_tx_columns[col_id];
 	const struct rs_tx_column *curr_column = &rs_tx_columns[tbl->column];
-	u32 sz = (sizeof(struct iwl_scale_tbl_info) -
-		  (sizeof(struct iwl_rate_scale_data) * IWL_RATE_COUNT));
 	unsigned long rate_mask = 0;
 	u32 rate_idx = 0;

-	memcpy(search_tbl, tbl, sz);
+	memcpy(search_tbl, tbl, offsetof(struct iwl_scale_tbl_info, win));

 	rate->sgi = column->sgi;
 	rate->ant = column->ant;
-- 
2.14.1