libinterfork: disable signals while forking and running ust_fork()

diff --git a/libinterfork/interfork.c b/libinterfork/interfork.c
index cfdd2c475b79ae016ff470c0bb04a4dd0b358bf2..26a8bd6ad9f314525b6cc9b079d0fb03fd295ef5 100644 (file)
--- a/libinterfork/interfork.c
+++ b/libinterfork/interfork.c
@@ -19,6 +19,7 @@
 #include <dlfcn.h>
 #include <unistd.h>
 #include <stdio.h>
+#include <signal.h>
 #include "share/usterr.h"
 
 extern void ust_fork(void);
@@ -30,6 +31,10 @@ pid_t fork(void)
 
        pid_t retval;
 
+       int result;
+       sigset_t all_sigs;
+       sigset_t orig_sigs;
+
        if(plibc_func == NULL) {
                plibc_func = dlsym(RTLD_NEXT, "fork");
                if(plibc_func == NULL) {
@@ -38,10 +43,38 @@ pid_t fork(void)
                }
        }
 
+       /* Disable interrupts. This is to avoid that the child
+        * intervenes before it is properly setup for tracing. It is
+        * safer to disable all signals, because then we know we are not
+        * breaking anything by restoring the original mask.
+        */
+
+       /* FIXME:
+               - only do this if tracing is active
+       */
+
+       /* Disable signals */
+       sigfillset(&all_sigs);
+       result = sigprocmask(SIG_BLOCK, &all_sigs, &orig_sigs);
+       if(result == -1) {
+               PERROR("sigprocmask");
+               return -1;
+       }
+
+       /* Do the real fork */
        retval = plibc_func();
 
-       if(retval == 0)
+       if(retval == 0) {
+               /* child */
                ust_fork();
+       }
+
+       /* Restore signals */
+       result = sigprocmask(SIG_BLOCK, &orig_sigs, NULL);
+       if(result == -1) {
+               PERROR("sigprocmask");
+               return -1;
+       }
 
        return retval;
 }