| Message ID | ZVPQJIP26dIzRAr6@work |
|---|---|
| State | New |
| Headers | show |
| Series | [v2,next] hwmon: (aspeed-pwm-tacho) Fix -Wstringop-overflow warning in aspeed_create_fan_tach_channel() | expand |
On Tue, Nov 14, 2023 at 01:53:08PM -0600, Gustavo A. R. Silva wrote: > 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> Thanks for the v2! This looks good; it's able to pass back the error now. Reviewed-by: Kees Cook <keescook@chromium.org>
On Tue, Nov 14, 2023 at 01:53:08PM -0600, Gustavo A. R. Silva wrote: > 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: > Still messes the point. This isn't about "the compiler doesn't know that", it is a real bug which may result in out-of-bounds accesses. Oh, never mind, I'll just apply it. Guenter
On 11/15/23 07:12, Guenter Roeck wrote: > On Tue, Nov 14, 2023 at 01:53:08PM -0600, Gustavo A. R. Silva wrote: >> 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: >> > > Still messes the point. This isn't about "the compiler doesn't know that", > it is a real bug which may result in out-of-bounds accesses. Oh, I mentioned that in anticipation of people saying something in the tone of 'that's never going to happen.' :p However, if this is a real bug, it should probably be tagged for -stable. > > Oh, never mind, I'll just apply it. Thank you! -- Gustavo
diff --git a/drivers/hwmon/aspeed-pwm-tacho.c b/drivers/hwmon/aspeed-pwm-tacho.c index 997df4b40509..9a209e064e46 100644 --- a/drivers/hwmon/aspeed-pwm-tacho.c +++ b/drivers/hwmon/aspeed-pwm-tacho.c @@ -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]; }; @@ -737,7 +739,8 @@ 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, +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) @@ -746,11 +749,17 @@ static void aspeed_create_fan_tach_channel(struct aspeed_pwm_tacho_data *priv, 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; }
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> --- Changes in v2: - Pass `dev` to function aspeed_create_fan_tach_channel() and return -EINVAL in case of error. (Guenter) - Update changelog text. v1: - Link: https://lore.kernel.org/linux-hardening/ZVJ7JBFoULzY3VGx@work/ drivers/hwmon/aspeed-pwm-tacho.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-)