Return-Path: Received: from mail.kernel.org ([198.145.29.99]:59072 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727307AbeLKPmm (ORCPT ); Tue, 11 Dec 2018 10:42:42 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Takashi Iwai , Meelis Roos Subject: [PATCH 3.18 06/54] ALSA: ac97: Fix incorrect bit shift at AC97-SPSA control write Date: Tue, 11 Dec 2018 16:40:54 +0100 Message-Id: <20181211151546.334247223@linuxfoundation.org> In-Reply-To: <20181211151546.010073210@linuxfoundation.org> References: <20181211151546.010073210@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Takashi Iwai commit 7194eda1ba0872d917faf3b322540b4f57f11ba5 upstream. The function snd_ac97_put_spsa() gets the bit shift value from the associated private_value, but it extracts too much; the current code extracts 8 bit values in bits 8-15, but this is a combination of two nibbles (bits 8-11 and bits 12-15) for left and right shifts. Due to the incorrect bits extraction, the actual shift may go beyond the 32bit value, as spotted recently by UBSAN check: UBSAN: Undefined behaviour in sound/pci/ac97/ac97_codec.c:836:7 shift exponent 68 is too large for 32-bit type 'int' This patch fixes the shift value extraction by masking the properly with 0x0f instead of 0xff. Reported-and-tested-by: Meelis Roos Cc: Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- sound/pci/ac97/ac97_codec.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/sound/pci/ac97/ac97_codec.c +++ b/sound/pci/ac97/ac97_codec.c @@ -829,7 +829,7 @@ static int snd_ac97_put_spsa(struct snd_ { struct snd_ac97 *ac97 = snd_kcontrol_chip(kcontrol); int reg = kcontrol->private_value & 0xff; - int shift = (kcontrol->private_value >> 8) & 0xff; + int shift = (kcontrol->private_value >> 8) & 0x0f; int mask = (kcontrol->private_value >> 16) & 0xff; // int invert = (kcontrol->private_value >> 24) & 0xff; unsigned short value, old, new;