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daemon: Remove redundant fork in commandrvf

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Currently the code is doing a redundant fork when passed the
COMMAND_FLAG_CHROOT_COPY_FILE_TO_STDIN flag. The additional
sub-process does a chroot() which has no effect because all file
handles are already open at that point, then simply copies its input
to its output.

This change simply replaces the above with a dup2 of the passed file
handle to STDIN of the command process.

RWMJ:
  Don't initialize 'pid' variable.
This commit is contained in:
Matthew Booth
2012-12-13 15:22:39 +00:00
committed by Richard W.M. Jones
parent d7a806ca1a
commit 2aa731e7c4
1 changed files with 7 additions and 82 deletions
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89
daemon/guestfsd.c
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@@ -789,8 +789,8 @@ commandrvf (char **stdoutput, char **stderror, int flags,
size_t so_size = 0, se_size = 0;
int so_fd[2], se_fd[2];
int flag_copy_stdin = flags & COMMAND_FLAG_CHROOT_COPY_FILE_TO_STDIN;
int stdin_fd[2] = { -1, -1 };
pid_t pid, stdin_pid = -1;
int flag_copy_fd = flags & COMMAND_FLAG_FD_MASK;
pid_t pid;
int r, quit, i;
fd_set rset, rset2;
char buf[256];
@@ -820,13 +820,6 @@ commandrvf (char **stdoutput, char **stderror, int flags,
abort ();
}
if (flag_copy_stdin) {
if (pipe (stdin_fd) == -1) {
error (0, errno, "pipe");
abort ();
}
}
pid = fork ();
if (pid == -1) {
error (0, errno, "fork");
@@ -838,9 +831,7 @@ commandrvf (char **stdoutput, char **stderror, int flags,
signal (SIGPIPE, SIG_DFL);
close (0);
if (flag_copy_stdin) {
dup2 (stdin_fd[PIPE_READ], STDIN_FILENO);
close (stdin_fd[PIPE_READ]);
close (stdin_fd[PIPE_WRITE]);
dup2 (flag_copy_fd, STDIN_FILENO);
} else {
/* Set stdin to /dev/null (ignore failure) */
ignore_value (open ("/dev/null", O_RDONLY|O_CLOEXEC));
@@ -862,60 +853,6 @@ commandrvf (char **stdoutput, char **stderror, int flags,
_exit (EXIT_FAILURE);
}
if (flag_copy_stdin) {
int fd = flags & COMMAND_FLAG_FD_MASK;
stdin_pid = fork ();
if (stdin_pid == -1) {
error (0, errno, "fork");
abort ();
}
if (stdin_pid == 0) { /* Child process copying stdin. */
close (so_fd[PIPE_READ]);
close (so_fd[PIPE_WRITE]);
close (se_fd[PIPE_READ]);
close (se_fd[PIPE_WRITE]);
close (STDOUT_FILENO);
dup2 (stdin_fd[PIPE_WRITE], STDOUT_FILENO);
close (stdin_fd[PIPE_READ]);
close (stdin_fd[PIPE_WRITE]);
if (chroot (sysroot) == -1) {
perror ("chroot");
_exit (EXIT_FAILURE);
}
ssize_t n;
char buffer[BUFSIZ];
while ((n = read (fd, buffer, sizeof buffer)) > 0) {
if (xwrite (STDOUT_FILENO, buffer, n) == -1)
/* EPIPE error indicates the command process has exited
* early. If the command process fails that will be caught
* by the daemon, and if not, then it's not an error.
*/
_exit (errno == EPIPE ? EXIT_SUCCESS : EXIT_FAILURE);
}
if (n == -1) {
perror ("read");
_exit (EXIT_FAILURE);
}
if (close (fd) == -1) {
perror ("close");
_exit (EXIT_FAILURE);
}
_exit (EXIT_SUCCESS);
}
close (fd);
close (stdin_fd[PIPE_READ]);
close (stdin_fd[PIPE_WRITE]);
}
/* Parent process. */
close (so_fd[PIPE_WRITE]);
close (se_fd[PIPE_WRITE]);
@@ -952,8 +889,8 @@ commandrvf (char **stdoutput, char **stderror, int flags,
}
close (so_fd[PIPE_READ]);
close (se_fd[PIPE_READ]);
if (flag_copy_stdin) close (flag_copy_fd);
waitpid (pid, NULL, 0);
if (stdin_pid >= 0) waitpid (stdin_pid, NULL, 0);
return -1;
}
@@ -1035,21 +972,9 @@ commandrvf (char **stdoutput, char **stderror, int flags,
}
}
if (flag_copy_stdin) {
/* Check copy process didn't fail. */
if (waitpid (stdin_pid, &r, 0) != stdin_pid) {
perror ("waitpid");
kill (pid, 9);
waitpid (pid, NULL, 0);
return -1;
}
if (!WIFEXITED (r) || WEXITSTATUS (r) != 0) {
fprintf (stderr, "failed copying from input file, see earlier messages (r = %d)\n", r);
kill (pid, 9);
waitpid (pid, NULL, 0);
return -1;
}
if (flag_copy_stdin && close (flag_copy_fd) == -1) {
perror ("close");
return -1;
}
/* Get the exit status of the command. */