CVE-2022-49612power: supply: core: Fix boundary conditions in interpolation

Official description

In the Linux kernel, the following vulnerability has been resolved: power: supply: core: Fix boundary conditions in interpolation The functions power_supply_temp2resist_simple and power_supply_ocv2cap_simple handle boundary conditions incorrectly. The change was introduced in a4585ba2050f460f749bbaf2b67bd56c41e30283 ("power: supply: core: Use library interpolation"). There are two issues: First, the lines "high = i - 1" and "high = i" in ocv2cap have the wrong order compared to temp2resist. As a consequence, ocv2cap sets high=-1 if ocv>table[0].ocv, which causes an out-of-bounds read. Second, the logic of temp2resist is also not correct. Consider the case table[] = {{20, 100}, {10, 80}, {0, 60}}. For temp=5, we expect a resistance of 70% by interpolation. However, temp2resist sets high=low=2 and returns 60.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/a762cee5d933fe4e2e1b773d60fc74fb8248d8c4
• https://git.kernel.org/stable/c/093d27bb6f2d1963f927ef59c9a2d37059175426