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hwmon: (lenovo-ec-sensors): Fix EC "MCHP" signature validation logic

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The EC signature check uses && instead of || between the four
byte comparisons.  With &&, the condition is true only when ALL
four bytes fail to match simultaneously, meaning the driver
accepts a device as a valid Microchip EC if ANY single byte of
the 4-byte "MCHP" signature happens to match.

Due to short-circuit evaluation, if the first byte reads back as
'M' (0x4D, a very common register value), the remaining three
comparisons are skipped entirely and the device is accepted.

Change && to || so the check rejects devices that do not fully
match the expected EC signature, as originally intended.

Fixes: 70118f85e6 ("hwmon: Add EC Chip driver for Lenovo ThinkStation motherboards")
Reviewed-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Signed-off-by: Kean Ren <rh_king@163.com>
Link: https://lore.kernel.org/r/20260521035228.533317-3-rh_king@163.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Kean Ren 2026-05-21 11:52:28 +08:00 committed by Guenter Roeck
parent 6c4e001cb0
commit e6056b1f5a
1 changed files with 3 additions and 3 deletions
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6
drivers/hwmon/lenovo-ec-sensors.c
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@ -537,9 +537,9 @@ static int lenovo_ec_probe(struct platform_device *pdev)
outw_p(MCHP_SING_IDX, MCHP_EMI0_EC_ADDRESS);
mutex_unlock(&ec_data->mec_mutex);
if ((inb_p(MCHP_EMI0_EC_DATA_BYTE0) != 'M') &&
(inb_p(MCHP_EMI0_EC_DATA_BYTE1) != 'C') &&
(inb_p(MCHP_EMI0_EC_DATA_BYTE2) != 'H') &&
if ((inb_p(MCHP_EMI0_EC_DATA_BYTE0) != 'M') ||
(inb_p(MCHP_EMI0_EC_DATA_BYTE1) != 'C') ||
(inb_p(MCHP_EMI0_EC_DATA_BYTE2) != 'H') ||
(inb_p(MCHP_EMI0_EC_DATA_BYTE3) != 'P'))
return -ENODEV;