start-stop-daemon: make --exec follow symlinks

by Joakim Tjernlund <joakim.tjernlund AT transmode.se>

function                                             old     new   delta
check                                               1591    1618     +27
start_stop_daemon_main                               770     792     +22

diff --git a/debianutils/start_stop_daemon.c b/debianutils/start_stop_daemon.c
index 601fd72..2f8e04a 100644 (file)
--- a/debianutils/start_stop_daemon.c
+++ b/debianutils/start_stop_daemon.c
@@ -32,6 +32,7 @@ struct globals {
        int user_id;
        smallint quiet;
        smallint signal_nr;
+       struct stat execstat;
 };
 #define G (*(struct globals*)&bb_common_bufsiz1)
 #define found             (G.found               )
@@ -42,6 +43,7 @@ struct globals {
 #define user_id           (G.user_id             )
 #define quiet             (G.quiet               )
 #define signal_nr         (G.signal_nr           )
+#define execstat          (G.execstat            )
 #define INIT_G() \
         do { \
                user_id = -1; \
@@ -49,22 +51,18 @@ struct globals {
         } while (0)
 
 
-static int pid_is_exec(pid_t pid, const char *name)
+static int pid_is_exec(pid_t pid)
 {
+       struct stat st;
        char buf[sizeof("/proc//exe") + sizeof(int)*3];
-       char *execbuf;
-       int n;
 
        sprintf(buf, "/proc/%u/exe", pid);
-       n = strlen(name) + 1;
-       execbuf = xzalloc(n + 1);
-       readlink(buf, execbuf, n);
-       /* if readlink fails because link target is longer than strlen(name),
-        * execbuf still contains "", and strcmp will return !0. */
-       n = strcmp(execbuf, name);
-       if (ENABLE_FEATURE_CLEAN_UP)
-               free(execbuf);
-       return !n; /* nonzero (true) if execbuf == name */
+       if (stat(buf, &st) < 0)
+               return 0;
+       if (st.st_dev == execstat.st_dev
+        && st.st_ino == execstat.st_ino)
+               return 1;
+       return 0;
 }
 
 static int pid_is_user(int pid, int uid)
@@ -104,7 +102,7 @@ static void check(int pid)
 {
        struct pid_list *p;
 
-       if (execname && !pid_is_exec(pid, execname)) {
+       if (execname && !pid_is_exec(pid)) {
                return;
        }
        if (userspec && !pid_is_user(pid, user_id)) {
@@ -300,6 +298,8 @@ int start_stop_daemon_main(int argc ATTRIBUTE_UNUSED, char **argv)
                if (errno)
                        user_id = xuname2uid(userspec);
        }
+       if (execname)
+               xstat(execname, &execstat);
 
        if (opt & CTX_STOP) {
                int i = do_stop();