[Libguestfs] [libnbd PATCH v3 04/19] socket activation: check syscalls for errors in the child process

[Laszlo Ersek]

It's bad hygiene to just assume dup2(), close() and signal() will succeed,
especially considering the inconsistency that we do check fcntl(). Check
all return values.

Signed-off-by: Laszlo Ersek <lersek at redhat.com>
Reviewed-by: Richard W.M. Jones <rjones at redhat.com>
---

Notes:
    v4:
    
    - pick up Rich's R-b
    
    context:-U12

 generator/states-connect-socket-activation.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/generator/states-connect-socket-activation.c b/generator/states-connect-socket-activation.c
index b9845c11a221..e3f7d05670b0 100644
--- a/generator/states-connect-socket-activation.c
+++ b/generator/states-connect-socket-activation.c
@@ -162,50 +162,59 @@  CONNECT_SA.START:
   }
 
   pid = fork ();
   if (pid == -1) {
     SET_NEXT_STATE (%.DEAD);
     set_error (errno, "fork");
     close (s);
     string_vector_empty (&env);
     return 0;
   }
   if (pid == 0) {         /* child - run command */
     if (s != FIRST_SOCKET_ACTIVATION_FD) {
-      dup2 (s, FIRST_SOCKET_ACTIVATION_FD);
-      close (s);
+      if (dup2 (s, FIRST_SOCKET_ACTIVATION_FD) == -1) {
+        nbd_internal_fork_safe_perror ("dup2");
+        _exit (126);
+      }
+      if (close (s) == -1) {
+        nbd_internal_fork_safe_perror ("close");
+        _exit (126);
+      }
     }
     else {
       /* We must unset CLOEXEC on the fd.  (dup2 above does this
        * implicitly because CLOEXEC is set on the fd, not on the
        * socket).
        */
       int flags = fcntl (s, F_GETFD, 0);
       if (flags == -1) {
         nbd_internal_fork_safe_perror ("fcntl: F_GETFD");
         _exit (126);
       }
       if (fcntl (s, F_SETFD, (int)(flags & ~(unsigned)FD_CLOEXEC)) == -1) {
         nbd_internal_fork_safe_perror ("fcntl: F_SETFD");
         _exit (126);
       }
     }
 
     char buf[32];
     const char *v =
       nbd_internal_fork_safe_itoa ((long) getpid (), buf, sizeof buf);
     strcpy (&env.ptr[0][PREFIX_LENGTH], v);
 
     /* Restore SIGPIPE back to SIG_DFL. */
-    signal (SIGPIPE, SIG_DFL);
+    if (signal (SIGPIPE, SIG_DFL) == SIG_ERR) {
+      nbd_internal_fork_safe_perror ("signal");
+      _exit (126);
+    }
 
     environ = env.ptr;
     execvp (h->argv.ptr[0], h->argv.ptr);
     nbd_internal_fork_safe_perror (h->argv.ptr[0]);
     if (errno == ENOENT)
       _exit (127);
     else
       _exit (126);
   }
 
   /* Parent. */
   close (s);