From: Dorian Rudolph mail@dorianrudolph.com
commit 093d27bb6f2d1963f927ef59c9a2d37059175426 upstream.
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.
Cc: stable@vger.kernel.org Signed-off-by: Dorian Rudolph mail@dorianrudolph.com Reviewed-by: Linus Walleij linus.walleij@linaro.org Fixes: a4585ba2050f ("power: supply: core: Use library interpolation") Signed-off-by: Sebastian Reichel sebastian.reichel@collabora.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/power/supply/power_supply_core.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-)
--- a/drivers/power/supply/power_supply_core.c +++ b/drivers/power/supply/power_supply_core.c @@ -846,17 +846,17 @@ int power_supply_temp2resist_simple(stru { int i, high, low;
- /* Break loop at table_len - 1 because that is the highest index */ - for (i = 0; i < table_len - 1; i++) + for (i = 0; i < table_len; i++) if (temp > table[i].temp) break;
/* The library function will deal with high == low */ - if ((i == 0) || (i == (table_len - 1))) - high = i; + if (i == 0) + high = low = i; + else if (i == table_len) + high = low = i - 1; else - high = i - 1; - low = i; + high = (low = i) - 1;
return fixp_linear_interpolate(table[low].temp, table[low].resistance, @@ -958,17 +958,17 @@ int power_supply_ocv2cap_simple(struct p { int i, high, low;
- /* Break loop at table_len - 1 because that is the highest index */ - for (i = 0; i < table_len - 1; i++) + for (i = 0; i < table_len; i++) if (ocv > table[i].ocv) break;
/* The library function will deal with high == low */ - if ((i == 0) || (i == (table_len - 1))) - high = i - 1; + if (i == 0) + high = low = i; + else if (i == table_len) + high = low = i - 1; else - high = i; /* i.e. i == 0 */ - low = i; + high = (low = i) - 1;
return fixp_linear_interpolate(table[low].ocv, table[low].capacity,