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hwmon: (aspeed-pwm-tacho) Fix -Wstringop-overflow warning in aspeed_create_fan_tach_channel()

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Based on the documentation below, the maximum number of Fan tach
channels is 16:

Documentation/devicetree/bindings/hwmon/aspeed-pwm-tacho.txt:45:
 45 - aspeed,fan-tach-ch : should specify the Fan tach input channel.
 46                 integer value in the range 0 through 15, with 0 indicating
 47                 Fan tach channel 0 and 15 indicating Fan tach channel 15.
 48                 At least one Fan tach input channel is required.

However, the compiler doesn't know that, and legitimaly warns about a potential
overwrite in array `u8 fan_tach_ch_source[16]` in `struct aspeed_pwm_tacho_data`,
in case `index` takes a value outside the boundaries of the array:

drivers/hwmon/aspeed-pwm-tacho.c:
179 struct aspeed_pwm_tacho_data {
...
184         bool fan_tach_present[16];
...
193         u8 fan_tach_ch_source[16];
196 };

In function ‘aspeed_create_fan_tach_channel’,
    inlined from ‘aspeed_create_fan’ at drivers/hwmon/aspeed-pwm-tacho.c:877:2,
    inlined from ‘aspeed_pwm_tacho_probe’ at drivers/hwmon/aspeed-pwm-tacho.c:936:9:
drivers/hwmon/aspeed-pwm-tacho.c:751:49: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
  751 |                 priv->fan_tach_ch_source[index] = pwm_source;
      |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~
drivers/hwmon/aspeed-pwm-tacho.c: In function ‘aspeed_pwm_tacho_probe’:
drivers/hwmon/aspeed-pwm-tacho.c:193:12: note: at offset [48, 255] into destination object ‘fan_tach_ch_source’ of size 16
  193 |         u8 fan_tach_ch_source[16];
      |            ^~~~~~~~~~~~~~~~~~

Fix this by sanity checking `index` before using it to index arrays of
size 16 elements in `struct aspeed_pwm_tacho_data`. Also, pass `dev` as
argument to function `aspeed_create_fan_tach_channel()`, and add an error
message in case `index` is out-of-bounds, in which case return `-EINVAL`.

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/ZVPQJIP26dIzRAr6@work
[groeck: Fixed continuation line alignment]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Gustavo A. R. Silva 2023-11-14 13:53:08 -06:00 committed by Guenter Roeck
parent 10bd80e0b3
commit b0d51ada88
1 changed files with 19 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
drivers/hwmon/aspeed-pwm-tacho.c
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@ -166,6 +166,8 @@
#define MAX_CDEV_NAME_LEN 16
#define MAX_ASPEED_FAN_TACH_CHANNELS 16
struct aspeed_cooling_device {
char name[16];
struct aspeed_pwm_tacho_data *priv;
@ -181,7 +183,7 @@ struct aspeed_pwm_tacho_data {
struct reset_control *rst;
unsigned long clk_freq;
bool pwm_present[8];
bool fan_tach_present[16];
bool fan_tach_present[MAX_ASPEED_FAN_TACH_CHANNELS];
u8 type_pwm_clock_unit[3];
u8 type_pwm_clock_division_h[3];
u8 type_pwm_clock_division_l[3];
@ -190,7 +192,7 @@ struct aspeed_pwm_tacho_data {
u16 type_fan_tach_unit[3];
u8 pwm_port_type[8];
u8 pwm_port_fan_ctrl[8];
u8 fan_tach_ch_source[16];
u8 fan_tach_ch_source[MAX_ASPEED_FAN_TACH_CHANNELS];
struct aspeed_cooling_device *cdev[8];
const struct attribute_group *groups[3];
};
@ -737,20 +739,27 @@ static void aspeed_create_pwm_port(struct aspeed_pwm_tacho_data *priv,
aspeed_set_pwm_port_fan_ctrl(priv, pwm_port, INIT_FAN_CTRL);
}
static void aspeed_create_fan_tach_channel(struct aspeed_pwm_tacho_data *priv,
u8 *fan_tach_ch,
int count,
u8 pwm_source)
static int aspeed_create_fan_tach_channel(struct device *dev,
struct aspeed_pwm_tacho_data *priv,
u8 *fan_tach_ch,
int count,
u8 pwm_source)
{
u8 val, index;
for (val = 0; val < count; val++) {
index = fan_tach_ch[val];
if (index >= MAX_ASPEED_FAN_TACH_CHANNELS) {
dev_err(dev, "Invalid Fan Tach input channel %u\n.", index);
return -EINVAL;
}
aspeed_set_fan_tach_ch_enable(priv->regmap, index, true);
priv->fan_tach_present[index] = true;
priv->fan_tach_ch_source[index] = pwm_source;
aspeed_set_fan_tach_ch_source(priv->regmap, index, pwm_source);
}
return 0;
}
static int
@ -874,7 +883,10 @@ static int aspeed_create_fan(struct device *dev,
fan_tach_ch, count);
if (ret)
return ret;
aspeed_create_fan_tach_channel(priv, fan_tach_ch, count, pwm_port);
ret = aspeed_create_fan_tach_channel(dev, priv, fan_tach_ch, count, pwm_port);
if (ret)
return ret;
return 0;
}