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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org, Denis Kirjanov <kda@linux-powerpc.org>,
        "=?UTF-8?Q?Rafa=C5=82=20?= =?UTF-8?Q?Mi=C5=82ecki?=" 
        <zajec5@gmail.com>, "Larry Finger" <Larry.Finger@lwfinger.net>,
        "Priit Laes" <plaes@plaes.org>, "Kalle Valo" <kvalo@codeaurora.org>
Date:   Tue, 02 Apr 2019 14:38:27 +0100
Message-ID: <lsq.1554212307.610285593@decadent.org.uk>
Subject: [PATCH 3.16 20/99] b43: Fix error in cordic routine
In-Reply-To: <lsq.1554212307.17110877@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
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3.16.65-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Larry Finger <Larry.Finger@lwfinger.net>

commit 8ea3819c0bbef57a51d8abe579e211033e861677 upstream.

The cordic routine for calculating sines and cosines that was added in
commit 6f98e62a9f1b ("b43: update cordic code to match current specs")
contains an error whereby a quantity declared u32 can in fact go negative.

This problem was detected by Priit Laes who is switching b43 to use the
routine in the library functions of the kernel.

Fixes: 986504540306 ("b43: make cordic common (LP-PHY and N-PHY need it)")
Reported-by: Priit Laes <plaes@plaes.org>
Cc: Rafał Miłecki <zajec5@gmail.com>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Priit Laes <plaes@plaes.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 drivers/net/wireless/b43/phy_common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/net/wireless/b43/phy_common.c
+++ b/drivers/net/wireless/b43/phy_common.c
@@ -596,7 +596,7 @@ struct b43_c32 b43_cordic(int theta)
 	u8 i;
 	s32 tmp;
 	s8 signx = 1;
-	u32 angle = 0;
+	s32 angle = 0;
 	struct b43_c32 ret = { .i = 39797, .q = 0, };
 
 	while (theta > (180 << 16))