runit: fix chpst -n -N -u USER

busybox's chpst first switches user/group and then tries to call nice().
Once the root priviledges are dropped, process priority can only be lowered.
So negative nice values don't work anymore.
Upstream version of chpst correctly calls nice() before switching user.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 7 insertions, 6 deletions

diff --git a/runit/chpst.c b/runit/chpst.c
index 846c846d3..ee3a33153 100644
--- a/runit/chpst.c
+++ b/runit/chpst.c
@@ -463,6 +463,13 @@ int chpst_main(int argc UNUSED_PARAM, char **argv)
                 xchroot(root);
         }
 
+        /* nice should be done before xsetuid */
+        if (opt & OPT_n) {
+                errno = 0;
+                if (nice(xatoi(nicestr)) == -1)
+                        bb_perror_msg_and_die("nice");
+        }
+
         if (opt & OPT_u) {
                 if (setgroups(1, &ugid.gid) == -1)
                         bb_perror_msg_and_die("setgroups");
@@ -470,12 +477,6 @@ int chpst_main(int argc UNUSED_PARAM, char **argv)
                 xsetuid(ugid.uid);
         }
 
-        if (opt & OPT_n) {
-                errno = 0;
-                if (nice(xatoi(nicestr)) == -1)
-                        bb_perror_msg_and_die("nice");
-        }
-
         if (opt & OPT_0)
                 close(STDIN_FILENO);
         if (opt & OPT_1)