Bug 2502528 (CVE-2026-64083)

In the Linux kernel, the following vulnerability has been resolved:

hwmon: (pmbus/adm1266) reject short block-read responses in the GPIO accessors

adm1266_gpio_get() and adm1266_gpio_get_multiple() both compose the
pin-status word as

	pins_status = read_buf[0] + (read_buf[1] << 8);

right after i2c_smbus_read_block_data(), guarding only against an
error return.  A well-behaved device returns 2 bytes for
GPIO_STATUS/PDIO_STATUS, but the helper happily reports a 0- or
1-byte response too.  If the device returns 0 bytes, both read_buf
slots are uninitialized stack memory; if it returns 1 byte, read_buf[1]
is.

The composed value then flows through set_bit() into the caller's
*bits in adm1266_gpio_get_multiple(), or into the return value of
adm1266_gpio_get(), and ends up in userspace via gpiolib (sysfs and
the char-dev ioctls).  That leaks a few bits of kernel stack per
request on any device whose firmware glitch, bus error, or hostile
slave produces a short block-read response.

Add the missing length check to both call sites and surface a short
response as -EIO.