linux-kernel - [PATCH] ALSA: usb-audio: fix sign unintended sign extension on left shifts

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Message-Id: <20190627164308.21286-1-colin.king@canonical.com>
Date:   Thu, 27 Jun 2019 17:43:08 +0100
From:   Colin King <colin.king@...onical.com>
To:     Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>,
        alsa-devel@...a-project.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] ALSA: usb-audio: fix sign unintended sign extension on left shifts

From: Colin Ian King <colin.king@...onical.com>

There are a couple of left shifts of unsigned 8 bit values that
first get promoted to signed ints and hence get sign extended
on the shift if the top bit of the 8 bit values are set. Fix
this by casting the 8 bit values to unsigned ints to stop the
unintentional sign extension.

Addresses-Coverity: ("Unintended sign extension")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 sound/usb/mixer_quirks.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sound/usb/mixer_quirks.c b/sound/usb/mixer_quirks.c
index 1f6011f36bb0..199fa157a411 100644
--- a/sound/usb/mixer_quirks.c
+++ b/sound/usb/mixer_quirks.c
@@ -741,7 +741,7 @@ static int snd_ni_control_init_val(struct usb_mixer_interface *mixer,
 		return err;
 	}
 
-	kctl->private_value |= (value << 24);
+	kctl->private_value |= ((unsigned int)value << 24);
 	return 0;
 }
 
@@ -902,7 +902,7 @@ static int snd_ftu_eff_switch_init(struct usb_mixer_interface *mixer,
 	if (err < 0)
 		return err;
 
-	kctl->private_value |= value[0] << 24;
+	kctl->private_value |= (unsigned int)value[0] << 24;
 	return 0;
 }
 
-- 
2.20.1