linux-kernel - [PATCH 05/11] i2c: ismt: Fix undefined behavior due to shift overflowing the constant

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Message-Id: <20220405151517.29753-6-bp@alien8.de>
Date:   Tue,  5 Apr 2022 17:15:11 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Seth Heasley <seth.heasley@...el.com>,
        Neil Horman <nhorman@...driver.com>,
        Wolfram Sang <wsa@...nel.org>, linux-i2c@...r.kernel.org
Subject: [PATCH 05/11] i2c: ismt: Fix undefined behavior due to shift overflowing the constant

From: Borislav Petkov <bp@...e.de>

Fix:

  drivers/i2c/busses/i2c-ismt.c: In function ‘ismt_hw_init’:
  drivers/i2c/busses/i2c-ismt.c:770:2: error: case label does not reduce to an integer constant
    case ISMT_SPGT_SPD_400K:
    ^~~~
  drivers/i2c/busses/i2c-ismt.c:773:2: error: case label does not reduce to an integer constant
    case ISMT_SPGT_SPD_1M:
    ^~~~

See https://lore.kernel.org/r/YkwQ6%2BtIH8GQpuct@zn.tnic for the gory
details as to why it triggers with older gccs only.

Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Seth Heasley <seth.heasley@...el.com>
Cc: Neil Horman <nhorman@...driver.com>
Cc: Wolfram Sang <wsa@...nel.org>
Cc: linux-i2c@...r.kernel.org
---
 drivers/i2c/busses/i2c-ismt.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-ismt.c b/drivers/i2c/busses/i2c-ismt.c
index f4820fd3dc13..c0364314877e 100644
--- a/drivers/i2c/busses/i2c-ismt.c
+++ b/drivers/i2c/busses/i2c-ismt.c
@@ -145,8 +145,8 @@
 #define ISMT_SPGT_SPD_MASK	0xc0000000	/* SMBus Speed mask */
 #define ISMT_SPGT_SPD_80K	0x00		/* 80 kHz */
 #define ISMT_SPGT_SPD_100K	(0x1 << 30)	/* 100 kHz */
-#define ISMT_SPGT_SPD_400K	(0x2 << 30)	/* 400 kHz */
-#define ISMT_SPGT_SPD_1M	(0x3 << 30)	/* 1 MHz */
+#define ISMT_SPGT_SPD_400K	(0x2U << 30)	/* 400 kHz */
+#define ISMT_SPGT_SPD_1M	(0x3U << 30)	/* 1 MHz */
 
 
 /* MSI Control Register (MSICTL) bit definitions */
-- 
2.35.1