1 files changed, 42 insertions, 38 deletions

diff --git a/archival/tar.c b/archival/tar.c
index e1af27401..9a171ceea 100644
--- a/archival/tar.c
+++ b/archival/tar.c
@@ -601,35 +601,46 @@ static int FAST_FUNC writeFileToTarball(const char *fileName, struct stat *statb
 /* Don't inline: vfork scares gcc and pessimizes code */
 static void NOINLINE vfork_compressor(int tar_fd, const char *gzip)
 {
-        pid_t gzipPid;
-
         // On Linux, vfork never unpauses parent early, although standard
         // allows for that. Do we want to waste bytes checking for it?
 #  define WAIT_FOR_CHILD 0
         volatile int vfork_exec_errno = 0;
-        struct fd_pair gzipDataPipe;
+        struct fd_pair data;
 #  if WAIT_FOR_CHILD
-        struct fd_pair gzipStatusPipe;
-        xpiped_pair(gzipStatusPipe);
+        struct fd_pair status;
+        xpiped_pair(status);
 #  endif
-        xpiped_pair(gzipDataPipe);
+        xpiped_pair(data);
 
         signal(SIGPIPE, SIG_IGN); /* we only want EPIPE on errors */
 
-        gzipPid = xvfork();
-
-        if (gzipPid == 0) {
+        if (xvfork() == 0) {
                 /* child */
+                int tfd;
                 /* NB: close _first_, then move fds! */
-                close(gzipDataPipe.wr);
+                close(data.wr);
 #  if WAIT_FOR_CHILD
-                close(gzipStatusPipe.rd);
-                /* gzipStatusPipe.wr will close only on exec -
+                close(status.rd);
+                /* status.wr will close only on exec -
                  * parent waits for this close to happen */
-                fcntl(gzipStatusPipe.wr, F_SETFD, FD_CLOEXEC);
+                fcntl(status.wr, F_SETFD, FD_CLOEXEC);
 #  endif
-                xmove_fd(gzipDataPipe.rd, 0);
-                xmove_fd(tar_fd, 1);
+                /* copy it: parent's tar_fd variable must not change */
+                tfd = tar_fd;
+                if (tfd == 0) {
+                        /* Output tar fd may be zero.
+                         * xmove_fd(data.rd, 0) would destroy it.
+                         * Reproducer:
+                         *  exec 0>&-
+                         *  exec 1>&-
+                         *  tar czf Z.tar.gz FILE
+                         * Swapping move_fd's order wouldn't work:
+                         * data.rd is 1 and _it_ would be destroyed.
+                         */
+                        tfd = dup(tfd);
+                }
+                xmove_fd(data.rd, 0);
+                xmove_fd(tfd, 1);
                 /* exec gzip/bzip2 program/applet */
                 BB_EXECLP(gzip, gzip, "-f", (char *)0);
                 vfork_exec_errno = errno;
@@ -637,20 +648,18 @@ static void NOINLINE vfork_compressor(int tar_fd, const char *gzip)
         }
 
         /* parent */
-        xmove_fd(gzipDataPipe.wr, tar_fd);
-        close(gzipDataPipe.rd);
+        xmove_fd(data.wr, tar_fd);
+        close(data.rd);
 #  if WAIT_FOR_CHILD
-        close(gzipStatusPipe.wr);
+        close(status.wr);
         while (1) {
-                char buf;
-                int n;
-
                 /* Wait until child execs (or fails to) */
-                n = full_read(gzipStatusPipe.rd, &buf, 1);
+                char buf;
+                int n = full_read(status.rd, &buf, 1);
                 if (n < 0 /* && errno == EAGAIN */)
                         continue;       /* try it again */
         }
-        close(gzipStatusPipe.rd);
+        close(status.rd);
 #  endif
         if (vfork_exec_errno) {
                 errno = vfork_exec_errno;
@@ -754,11 +763,7 @@ static NOINLINE int writeTarFile(
         return errorFlag;
 }
 
-#else /* !FEATURE_TAR_CREATE */
-
-# define writeTarFile(...) 0
-
-#endif
+#endif /* FEATURE_TAR_CREATE */
 
 #if ENABLE_FEATURE_TAR_FROM
 static llist_t *append_file_list_to_list(llist_t *list)
@@ -1190,17 +1195,16 @@ int tar_main(int argc UNUSED_PARAM, char **argv)
                 if (LONE_DASH(tar_filename)) {
                         tar_handle->src_fd = tar_fd;
                         tar_handle->seek = seek_by_read;
+                } else
+                if (ENABLE_FEATURE_TAR_AUTODETECT
+                 && flags == O_RDONLY
+                 && !(opt & OPT_ANY_COMPRESS)
+                ) {
+                        tar_handle->src_fd = open_zipped(tar_filename, /*fail_if_not_compressed:*/ 0);
+                        if (tar_handle->src_fd < 0)
+                                bb_perror_msg_and_die("can't open '%s'", tar_filename);
                 } else {
-                        if (ENABLE_FEATURE_TAR_AUTODETECT
-                         && flags == O_RDONLY
-                         && !(opt & OPT_ANY_COMPRESS)
-                        ) {
-                                tar_handle->src_fd = open_zipped(tar_filename, /*fail_if_not_compressed:*/ 0);
-                                if (tar_handle->src_fd < 0)
-                                        bb_perror_msg_and_die("can't open '%s'", tar_filename);
-                        } else {
-                                tar_handle->src_fd = xopen(tar_filename, flags);
-                        }
+                        tar_handle->src_fd = xopen(tar_filename, flags);
                 }
         }