[PATCH v2] sysctl: fix the problem that no error is reported when access fails

[zhuyan (M)]

When an general user without authority sets the system configuration,
0 is returned, but the modification is not successful. It is unreasonable.

Such as, general user didn't have /proc/sys/fs/protected_hardlinks permissions, 
but run the command 'busybox sysctl fs.protected_symlinks',
0 is returned.

Signed-off-by: Yan Zhu <zhuya...@huawei.com>
---
 procps/sysctl.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/procps/sysctl.c b/procps/sysctl.c index 6d77185..0ffa9fe 100644
--- a/procps/sysctl.c
+++ b/procps/sysctl.c
@@ -53,6 +53,7 @@ enum {
        FLAG_QUIET           = 1 << 6,
 };
 #define OPTION_STR "neAapwq"
+bool sysctl_input_dir = false;
 
 static void sysctl_dots_to_slashes(char *name)  { @@ -170,6 +171,10 @@ static 
int sysctl_act_on_setting(char *setting)
        if (fd < 0) {
                switch (errno) {
                case EACCES:
+                       if (!sysctl_input_dir) {
+                               bb_perror_msg("error reading key '%s'", 
outname);
+                               break;
+                       }
                        /* Happens for write-only settings, e.g. 
net.ipv6.route.flush */
                        goto end;
                case ENOENT:
@@ -310,6 +315,7 @@ int sysctl_main(int argc UNUSED_PARAM, char **argv)  {
        int retval;
        int opt;
+       struct stat buf;
 
        opt = getopt32(argv, "+" OPTION_STR); /* '+' - stop on first non-option 
*/
        argv += optind;
@@ -331,6 +337,7 @@ int sysctl_main(int argc UNUSED_PARAM, char **argv)
        }
        xchdir("/proc/sys");
        if (opt & (FLAG_TABLE_FORMAT | FLAG_SHOW_ALL)) {
+               sysctl_input_dir = true;
                return sysctl_act_recursive(".");
        }
 
@@ -338,6 +345,12 @@ int sysctl_main(int argc UNUSED_PARAM, char **argv)
 
        retval = 0;
        while (*argv) {
+               if (stat(*argv, &buf) == 0
+                && S_ISDIR(buf.st_mode))
+                       sysctl_input_dir = true;
+               else
+                       sysctl_input_dir = false;
+
                sysctl_dots_to_slashes(*argv);
                retval |= sysctl_act_recursive(*argv);
                argv++;
--
2.12.3

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