tools/thermal: Fix possible path truncations

A build with -D_FORTIFY_SOURCE=2 enabled will produce the following warnings:

sysfs.c:63:30: warning: '%s' directive output may be truncated writing up to 255 bytes into a region of size between 0 and 255 [-Wformat-truncation=]
  snprintf(filepath, 256, "%s/%s", path, filename);
                              ^~
Bump up the buffer to PATH_MAX which is the limit and account for all of
the possible NUL and separators that could lead to exceeding the
allocated buffer sizes.

Fixes: 94f69966faf8 ("tools/thermal: Introduce tmon, a tool for thermal subsystem")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/tools/thermal/tmon/sysfs.c b/tools/thermal/tmon/sysfs.c
index b00b1bf..cb1108b 100644 (file)
--- a/tools/thermal/tmon/sysfs.c
+++ b/tools/thermal/tmon/sysfs.c
@@ -13,6 +13,7 @@
 #include <stdint.h>
 #include <dirent.h>
 #include <libintl.h>
+#include <limits.h>
 #include <ctype.h>
 #include <time.h>
 #include <syslog.h>
@@ -33,9 +34,9 @@ int sysfs_set_ulong(char *path, char *filename, unsigned long val)
 {
        FILE *fd;
        int ret = -1;
-       char filepath[256];
+       char filepath[PATH_MAX + 2]; /* NUL and '/' */
 
-       snprintf(filepath, 256, "%s/%s", path, filename);
+       snprintf(filepath, sizeof(filepath), "%s/%s", path, filename);
 
        fd = fopen(filepath, "w");
        if (!fd) {
@@ -57,9 +58,9 @@ static int sysfs_get_ulong(char *path, char *filename, unsigned long *p_ulong)
 {
        FILE *fd;
        int ret = -1;
-       char filepath[256];
+       char filepath[PATH_MAX + 2]; /* NUL and '/' */
 
-       snprintf(filepath, 256, "%s/%s", path, filename);
+       snprintf(filepath, sizeof(filepath), "%s/%s", path, filename);
 
        fd = fopen(filepath, "r");
        if (!fd) {
@@ -76,9 +77,9 @@ static int sysfs_get_string(char *path, char *filename, char *str)
 {
        FILE *fd;
        int ret = -1;
-       char filepath[256];
+       char filepath[PATH_MAX + 2]; /* NUL and '/' */
 
-       snprintf(filepath, 256, "%s/%s", path, filename);
+       snprintf(filepath, sizeof(filepath), "%s/%s", path, filename);
 
        fd = fopen(filepath, "r");
        if (!fd) {
@@ -199,8 +200,8 @@ static int find_tzone_cdev(struct dirent *nl, char *tz_name,
 {
        unsigned long trip_instance = 0;
        char cdev_name_linked[256];
-       char cdev_name[256];
-       char cdev_trip_name[256];
+       char cdev_name[PATH_MAX];
+       char cdev_trip_name[PATH_MAX];
        int cdev_id;
 
        if (nl->d_type == DT_LNK) {
@@ -213,7 +214,8 @@ static int find_tzone_cdev(struct dirent *nl, char *tz_name,
                        return -EINVAL;
                }
                /* find the link to real cooling device record binding */
-               snprintf(cdev_name, 256, "%s/%s", tz_name, nl->d_name);
+               snprintf(cdev_name, sizeof(cdev_name) - 2, "%s/%s",
+                        tz_name, nl->d_name);
                memset(cdev_name_linked, 0, sizeof(cdev_name_linked));
                if (readlink(cdev_name, cdev_name_linked,
                                sizeof(cdev_name_linked) - 1) != -1) {
@@ -226,8 +228,8 @@ static int find_tzone_cdev(struct dirent *nl, char *tz_name,
                        /* find the trip point in which the cdev is binded to
                         * in this tzone
                         */
-                       snprintf(cdev_trip_name, 256, "%s%s", nl->d_name,
-                               "_trip_point");
+                       snprintf(cdev_trip_name, sizeof(cdev_trip_name) - 1,
+                               "%s%s", nl->d_name, "_trip_point");
                        sysfs_get_ulong(tz_name, cdev_trip_name,
                                        &trip_instance);
                        /* validate trip point range, e.g. trip could return -1