create_bundle(): duplicate file descriptor to avoid closing it twice

write_pack_data() passes bundle_fd to start_command() to be used as
the stdout of pack-objects. But start_command() closes its stdout if
it is > 1. This is a problem if bundle_fd is the fd of a lock_file,
because commit_lock_file() will also try to close the fd.

So the old code suppressed commit_lock_file()'s usual behavior of
closing the file descriptor by setting the lock_file object's fd field
to -1.

But this is not really kosher. Code here shouldn't be mutating fields
within the lock_file object.

Instead, duplicate the file descriptor before passing it to
write_pack_data(). Then that function can close its copy without
closing the copy held in the lock_file object.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/bundle.c b/bundle.c
index f732c920aadd7515d56f7d344f771fb9d362f042..b9dacc0241f0c58244b62ddff137c85291c37dd0 100644 (file)
--- a/bundle.c
+++ b/bundle.c
@@ -235,7 +235,9 @@ out:
        return result;
 }
 
-static int write_pack_data(int bundle_fd, struct lock_file *lock, struct rev_info *revs)
+
+/* Write the pack data to bundle_fd, then close it if it is > 1. */
+static int write_pack_data(int bundle_fd, struct rev_info *revs)
 {
        struct child_process pack_objects = CHILD_PROCESS_INIT;
        int i;
@@ -250,13 +252,6 @@ static int write_pack_data(int bundle_fd, struct lock_file *lock, struct rev_inf
        if (start_command(&pack_objects))
                return error(_("Could not spawn pack-objects"));
 
-       /*
-        * start_command closed bundle_fd if it was > 1
-        * so set the lock fd to -1 so commit_lock_file()
-        * won't fail trying to close it.
-        */
-       lock->fd = -1;
-
        for (i = 0; i < revs->pending.nr; i++) {
                struct object *object = revs->pending.objects[i].item;
                if (object->flags & UNINTERESTING)
@@ -416,10 +411,21 @@ int create_bundle(struct bundle_header *header, const char *path,
        bundle_to_stdout = !strcmp(path, "-");
        if (bundle_to_stdout)
                bundle_fd = 1;
-       else
+       else {
                bundle_fd = hold_lock_file_for_update(&lock, path,
                                                      LOCK_DIE_ON_ERROR);
 
+               /*
+                * write_pack_data() will close the fd passed to it,
+                * but commit_lock_file() will also try to close the
+                * lockfile's fd. So make a copy of the file
+                * descriptor to avoid trying to close it twice.
+                */
+               bundle_fd = dup(bundle_fd);
+               if (bundle_fd < 0)
+                       die_errno("unable to dup file descriptor");
+       }
+
        /* write signature */
        write_or_die(bundle_fd, bundle_signature, strlen(bundle_signature));
 
@@ -445,7 +451,7 @@ int create_bundle(struct bundle_header *header, const char *path,
                return -1;
 
        /* write pack */
-       if (write_pack_data(bundle_fd, &lock, &revs))
+       if (write_pack_data(bundle_fd, &revs))
                return -1;
 
        if (!bundle_to_stdout) {