Affected: Linux

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

hwmon: (ltc4282) Clamp negative current limits

When a negative value is passed to ltc4282_write_curr(), the signed long val is cast directly to u64:

drivers/hwmon/ltc4282.c:ltc4282_write_curr() { /* need to pass it in millivolt */ u32 in = DIV_ROUND_CLOSEST_ULL((u64)val * st->rsense, DECA * MICRO); ... }

This cast converts negative inputs into large positive values. The subsequent division result overflows the u32 in variable, truncating to a pseudo-random positive value. When this is passed to ltc4282_write_voltage_byte(), it is clamped to the maximum limit instead of zero.

Clamp val to 0 and to the maximum supported upper limit before the cast and assign the result to a 64-bit temporary variable before the division to avoid the underflow and an also possible overflow.