maildirlock: Do IPC with pipes instead of with signals. Fixes race conditions.

Based on patch by Kyle Wheeler.

--HG--
branch : HEAD

diff --git a/src/util/maildirlock.c b/src/util/maildirlock.c
index b0fe8b00781b09be0f14db0c911081b93948be96..4dbbace0c3cf6176e586cadfde225f9efe0816f1 100644 (file)
--- a/src/util/maildirlock.c
+++ b/src/util/maildirlock.c
@@ -3,6 +3,7 @@
 #include "lib.h"
 #include "lib-signals.h"
 #include "ioloop.h"
+#include "write-full.h"
 #include "file-dotlock.h"
 #include "maildir-uidlist.h"
 
@@ -22,11 +23,9 @@ static struct dotlock_settings dotlock_settings = {
 };
 
 static struct ioloop *ioloop;
-static bool success = FALSE;
 
-static void sig_die(int signo, void *context ATTR_UNUSED)
+static void sig_die(int signo ATTR_UNUSED, void *context ATTR_UNUSED)
 {
-       success = signo == SIGTERM;
        io_loop_stop(ioloop);
 }
 
@@ -46,6 +45,8 @@ int main(int argc, const char *argv[])
        struct dotlock *dotlock;
        unsigned int timeout;
        pid_t pid, parent_pid;
+       int fd[2], ret;
+       char c;
 
        if (argc != 3) {
                fprintf(stderr, "Usage: maildirlock <path> <timeout>\n"
@@ -53,6 +54,10 @@ int main(int argc, const char *argv[])
                return 1;
        }
        parent_pid = getpid();
+       if (pipe(fd) != 0) {
+               fprintf(stderr, "pipe() failed: %m");
+               return 1;
+       }
 
        pid = fork();
        if (pid == (pid_t)-1) {
@@ -62,17 +67,23 @@ int main(int argc, const char *argv[])
 
        /* call lib_init() only after fork so that PID gets set correctly */
        lib_init();
-       ioloop = io_loop_create();
        lib_signals_init();
+       ioloop = io_loop_create();
        lib_signals_set_handler(SIGINT, TRUE, sig_die, NULL);
        lib_signals_set_handler(SIGTERM, TRUE, sig_die, NULL);
-       lib_signals_set_handler(SIGCHLD, TRUE, sig_die, NULL);
 
        if (pid != 0) {
-               /* master - wait for the child process to finish locking */
-               io_loop_run(ioloop);
-               if (!success)
+               close(fd[1]);
+               ret = read(fd[0], &c, 1);
+               if (ret < 0) {
+                       fprintf(stderr, "read(pipe) failed: %m");
                        return 1;
+               }
+               if (ret != 1) {
+                       /* locking timed out */
+                       return 1;
+               }
+
                printf("%s", dec2str(pid));
                return 0;
        }
@@ -85,9 +96,10 @@ int main(int argc, const char *argv[])
        if (maildir_lock(argv[1], timeout, &dotlock) <= 0)
                return 1;
 
-       /* locked - send a  */
-       if (kill(parent_pid, SIGTERM) < 0)
-               i_fatal("kill(parent, SIGTERM) failed: %m");
+       /* locked - send a byte */
+       if (write_full(fd[1], "", 1) < 0)
+               i_fatal("write(pipe) failed: %m");
+
        io_loop_run(ioloop);
 
        file_dotlock_delete(&dotlock);