linux-kernel - Re: [PATCH] tools/thermal: Fix possible path truncations

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Date:   Wed, 3 Aug 2022 19:07:35 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Florian Fainelli <f.fainelli@...il.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Markus Mayer <mmayer@...adcom.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Amit Kucheria <amitk@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        "open list:THERMAL" <linux-pm@...r.kernel.org>
Subject: Re: [PATCH] tools/thermal: Fix possible path truncations

On Mon, Jul 25, 2022 at 7:38 PM Florian Fainelli <f.fainelli@...il.com> wrote:
>
> 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@...il.com>

Daniel, are you going to pick up this one or should I?

There is also a tmon patch from Florian that seems to be pending.
Should I take care of it?

> ---
>  tools/thermal/tmon/sysfs.c | 24 +++++++++++++-----------
>  1 file changed, 13 insertions(+), 11 deletions(-)
>
> diff --git a/tools/thermal/tmon/sysfs.c b/tools/thermal/tmon/sysfs.c
> index b00b1bfd9d8e..cb1108bc9249 100644
> --- 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
> --
> 2.25.1
>