[PATCH] 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 <zhuyan34 at huawei.com>
---
 procps/sysctl.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/procps/sysctl.c b/procps/sysctl.c index 6d77185..dd981f8 100644
--- a/procps/sysctl.c
+++ b/procps/sysctl.c
@@ -129,6 +129,7 @@ static int sysctl_act_on_setting(char *setting)
 	char *cptr, *outname;
 	char *value = value; /* for compiler */
 	bool writing = (option_mask32 & FLAG_WRITE);
+	bool read_all = (option_mask32 & FLAG_SHOW_ALL);
 
 	outname = xstrdup(setting);
 
@@ -170,6 +171,13 @@ static int sysctl_act_on_setting(char *setting)
 	if (fd < 0) {
 		switch (errno) {
 		case EACCES:
+			if (!read_all) {
+				bb_perror_msg("error %sing key '%s'",
+						writing ?
+							"sett" : "read",
+						outname);
+				break;
+			}
 			/* Happens for write-only settings, e.g. net.ipv6.route.flush */
 			goto end;
 		case ENOENT:
--
2.12.3