Hello! Mario wrote me about two I think security problems in dell-smm-hwmon driver and I would like to ask you, how to fix them. 1) File /proc/i8k (exists only when kernel is compiled with CONFIG_I8K) exports DMI_PRODUCT_SERIAL and it can be read by ordinary user, without root permission. Normally DMI_PRODUCT_SERIAL can be read from sysfs file /sys/class/dmi/id/product_serial but only by root user. 2) Via /proc/i8k ordinary user can set fan speed. This is because how "restricted" parameter and variable works. Setting fan speed by normal non-root user can be dangerous, e.g. malicious application under user "nobody" could take control of fans. Do you have idea how to fix these problems? Just to note that /proc/i8k has stable kernel ABI and changing it will break all existing i8k* applications. But /proc/i8k is there only for old legacy laptops (year 2000). There is module parameter "restricted" with default value false and description: "Allow fan control if SYS_ADMIN capability set". Current code do: case I8K_SET_FAN: if (restricted && !capable(CAP_SYS_ADMIN)) return -EPERM; For me description is a bit ambiguous. What about setting "restricted" by default to true and updating description to something like this? "Disallow fan control when SYS_ADMIN capability is not set (default: 1)" -- Pali Rohár pali.rohar@xxxxxxxxx
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