if pidfile turned out to be !regular file, do not unlink it.

It's most probably the /dev/null.

4 files changed, 25 insertions, 15 deletions

diff --git a/Config.in b/Config.in
index 54bcd9d10..24e461eb7 100644
--- a/Config.in
+++ b/Config.in
@@ -144,7 +144,7 @@ config FEATURE_PIDFILE
         bool "Support writing pidfiles"
         default n
         help
-          This option makes some applets (crond, syslogd and inetd) write
+          This option makes some applets (e.g. crond, syslogd, inetd) write
           a pidfile in /var/run. Some applications rely on them.
 
 config FEATURE_SUID
diff --git a/include/libbb.h b/include/libbb.h
index fc0a0ae6c..d60b410ae 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -622,12 +622,14 @@ llist_t *llist_rev(llist_t *list);
 /* start_stop_daemon and udhcpc are special - they want
  * to create pidfiles regardless of FEATURE_PIDFILE */
 #if ENABLE_FEATURE_PIDFILE || defined(WANT_PIDFILE)
-int write_pidfile(const char *path);
-#define remove_pidfile(f) ((void)unlink(f))
+/* True only if we created pidfile which is *file*, not /dev/null etc */
+extern smallint wrote_pidfile;
+void write_pidfile(const char *path);
+#define remove_pidfile(path) do { if (wrote_pidfile) unlink(path); } while (0)
 #else
-/* Why? #defining it to 1 gives "warning: statement with no effect"... */
-static ALWAYS_INLINE int write_pidfile(const char *path) { return 1; }
-#define remove_pidfile(f) ((void)0)
+enum { wrote_pidfile = 0 };
+#define write_pidfile(path)  ((void)0)
+#define remove_pidfile(path) ((void)0)
 #endif
 
 enum {
diff --git a/libbb/pidfile.c b/libbb/pidfile.c
index 64e67c322..cafa7891f 100644
--- a/libbb/pidfile.c
+++ b/libbb/pidfile.c
@@ -11,22 +11,30 @@
 #define WANT_PIDFILE 1
 #include "libbb.h"
 
-int write_pidfile(const char *path)
+smallint wrote_pidfile;
+
+void write_pidfile(const char *path)
 {
         int pid_fd;
         char *end;
         char buf[sizeof(int)*3 + 2];
+        struct stat sb;
 
         if (!path)
-                return 1;
+                return;
         /* we will overwrite stale pidfile */
         pid_fd = open(path, O_WRONLY|O_CREAT|O_TRUNC, 0666);
         if (pid_fd < 0)
-                return 0;
-        /* few bytes larger, but doesn't use stdio */
-        end = utoa_to_buf(getpid(), buf, sizeof(buf));
-        *end = '\n';
-        full_write(pid_fd, buf, end - buf + 1);
+                return;
+
+        /* path can be "/dev/null"! Test for such cases */
+        wrote_pidfile = (fstat(pid_fd, &sb) == 0) && S_ISREG(sb.st_mode);
+
+        if (wrote_pidfile) {
+                /* few bytes larger, but doesn't use stdio */
+                end = utoa_to_buf(getpid(), buf, sizeof(buf));
+                *end = '\n';
+                full_write(pid_fd, buf, end - buf + 1);
+        }
         close(pid_fd);
-        return 1;
 }
diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index 7cb1dfe5d..7d38742b9 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -546,7 +546,7 @@ int udhcpc_main(int argc, char **argv)
  ret0:
         retval = 0;
  ret:
-        if (client_config.pidfile)
+        /*if (client_config.pidfile) - remove_pidfile has it's own check */
                 remove_pidfile(client_config.pidfile);
         return retval;
 }