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SubjectRe: [PATCH 05/11] i2c: ismt: Fix undefined behavior due to shift overflowing the constant
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On Tue, 2022-04-05 at 17:15 +0200, Borislav Petkov wrote:
> From: Borislav Petkov <bp@suse.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@suse.de>
Reviewed-by: Seth Heasley <seth.heasley@intel.com>

> Cc: Seth Heasley <seth.heasley@intel.com>
> Cc: Neil Horman <nhorman@tuxdriver.com>
> Cc: Wolfram Sang <wsa@kernel.org>
> Cc: linux-i2c@vger.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 */

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