2023-10-25 12:23:41

by Zhang, Rui

Subject: [PATCH] hwmon: (coretemp) Fix potentially truncated sysfs attribute name

When build with W=1 and "-Werror=format-truncation", below error is
observed in coretemp driver,

drivers/hwmon/coretemp.c: In function 'create_core_data':
>> drivers/hwmon/coretemp.c:393:34: error: '%s' directive output may be truncated writing likely 5 or more bytes into a region of size between 3 and 13 [-Werror=format-truncation=]
393 | "temp%d_%s", attr_no, suffixes[i]);
| ^~
drivers/hwmon/coretemp.c:393:26: note: assuming directive output of 5 bytes
393 | "temp%d_%s", attr_no, suffixes[i]);
| ^~~~~~~~~~~
drivers/hwmon/coretemp.c:392:17: note: 'snprintf' output 7 or more bytes (assuming 22) into a destination of size 19
392 | snprintf(tdata->attr_name[i], CORETEMP_NAME_LENGTH,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
393 | "temp%d_%s", attr_no, suffixes[i]);
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors

Given that
1. '%d' could take 10 charactors,
2. '%s' could take 10 charactors ("crit_alarm"),
3. "temp", "_" and the NULL terminator take 6 charactors,
fix the problem by increasing CORETEMP_NAME_LENGTH to 28.

Signed-off-by: Zhang Rui <[email protected]>
Fixes: 7108b80a542b ("hwmon/coretemp: Handle large core ID value")
Reported-by: kernel test robot <[email protected]>
Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
---
Note that, in practice, I found that the problem is gone if I increase
the size to 22. But I cannot explain this.
---
drivers/hwmon/coretemp.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
index eba94f68585a..ba82d1e79c13 100644
--- a/drivers/hwmon/coretemp.c
+++ b/drivers/hwmon/coretemp.c
@@ -42,7 +42,7 @@ MODULE_PARM_DESC(tjmax, "TjMax value in degrees Celsius");
#define PKG_SYSFS_ATTR_NO 1 /* Sysfs attribute for package temp */
#define BASE_SYSFS_ATTR_NO 2 /* Sysfs Base attr no for coretemp */
#define NUM_REAL_CORES 128 /* Number of Real cores per cpu */
-#define CORETEMP_NAME_LENGTH 19 /* String Length of attrs */
+#define CORETEMP_NAME_LENGTH 28 /* String Length of attrs */
#define MAX_CORE_ATTRS 4 /* Maximum no of basic attrs */
#define TOTAL_ATTRS (MAX_CORE_ATTRS + 1)
#define MAX_CORE_DATA (NUM_REAL_CORES + BASE_SYSFS_ATTR_NO)
--
2.34.1

2023-10-25 18:58:32

by Guenter Roeck

Subject: Re: [PATCH] hwmon: (coretemp) Fix potentially truncated sysfs attribute name

On Wed, Oct 25, 2023 at 08:23:16PM +0800, Zhang Rui wrote:
> When build with W=1 and "-Werror=format-truncation", below error is
> observed in coretemp driver,
>
> drivers/hwmon/coretemp.c: In function 'create_core_data':
> >> drivers/hwmon/coretemp.c:393:34: error: '%s' directive output may be truncated writing likely 5 or more bytes into a region of size between 3 and 13 [-Werror=format-truncation=]
> 393 | "temp%d_%s", attr_no, suffixes[i]);
> | ^~
> drivers/hwmon/coretemp.c:393:26: note: assuming directive output of 5 bytes
> 393 | "temp%d_%s", attr_no, suffixes[i]);
> | ^~~~~~~~~~~
> drivers/hwmon/coretemp.c:392:17: note: 'snprintf' output 7 or more bytes (assuming 22) into a destination of size 19
> 392 | snprintf(tdata->attr_name[i], CORETEMP_NAME_LENGTH,
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 393 | "temp%d_%s", attr_no, suffixes[i]);
> | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> cc1: all warnings being treated as errors
>
> Given that
> 1. '%d' could take 10 charactors,
> 2. '%s' could take 10 charactors ("crit_alarm"),
> 3. "temp", "_" and the NULL terminator take 6 charactors,
> fix the problem by increasing CORETEMP_NAME_LENGTH to 28.
>
> Signed-off-by: Zhang Rui <[email protected]>
> Fixes: 7108b80a542b ("hwmon/coretemp: Handle large core ID value")
> Reported-by: kernel test robot <[email protected]>
> Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/

Applied.

Thanks,
Guenter