[RFC PATCH] Fix index lock breakage in mailbox_release_resources()

[Thomas Jarosch]

mailbox_release_resources() closes the file descriptor
to the index. This implicitly releases any lock on the file.

Unfortunately the function does not reset the index_locktype state.
Therefore we didn't notice that a mailbox rename
operated on an unlocked index of the new mailbox. Yikes.

Fix it by resetting the lock state and also adapt
API users to properly lock the index. This change
might uncover more API abuse / break "working" code.

Note: mailbox_index_lock() implies a mailbox_read_index_header().
But it also does more work than just read the index header,
so there might be side effects.

Patch developed against 2.5 and is easily ported to 2.4 or git HEAD.
I'll resubmit patches for each branch once the general
concept of this change is approved.

---
 imap/mailbox.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/imap/mailbox.c b/imap/mailbox.c
index 51b8c9d..5b7bd9c 100644
--- a/imap/mailbox.c
+++ b/imap/mailbox.c
@@ -833,6 +833,7 @@ static void mailbox_release_resources(struct mailbox *mailbox)
 
     /* release and unmap index */
     xclose(mailbox->index_fd);
+    mailbox->index_locktype = 0;
     if (mailbox->index_base)
 	map_free(&mailbox->index_base, &mailbox->index_len);
 
@@ -4052,7 +4053,7 @@ HIDDEN int mailbox_rename_copy(struct mailbox *oldmailbox,
     if (r) goto fail;
 
     /* Re-open header file */
-    r = mailbox_read_index_header(newmailbox);
+    r = mailbox_lock_index(newmailbox, LOCK_EXCLUSIVE);
     if (r) goto fail;
 
     /* read in the flags */
@@ -4370,7 +4371,7 @@ static int mailbox_reconstruct_create(const char *name, struct mailbox **mbptr)
  
     /* Attempt to open index */
     r = mailbox_open_index(mailbox);
-    if (!r) r = mailbox_read_index_header(mailbox);
+    if (!r) r = mailbox_lock_index(mailbox, LOCK_EXCLUSIVE);
     if (r) {
 	printf("%s: failed to read index header\n", mailbox->name);
 	syslog(LOG_ERR, "failed to read index header for %s", mailbox->name);
-- 
1.9.3