Re: Another cache bug!

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--On December 10, 2008 10:36:56 AM +1100 Bron Gondwana <brong@xxxxxxxxxxx> wrote:

Wow, this is the thanks I get for doing sanity checks on files, find more
bugs!

This one is due to delayed expunge, plain and simple.  Cyrus decides what
cache records to copy during an IMAP COPY command by reading the cache
offsets for msgno and msgno+1 (or the end of the cache file if it's the
last msgno).

Obviously if some intervening messages have already been deleted from the
cyrus.index then it will be copying all those cache records as well to the
destination folder.  Oops.

The attached patch reworks mailbox_cache_size into two functions, the
second being mailbox_cache_size_detail that takes memory locations for
the cache mmap rather than a mailbox object (because imapd doesn't update
the locations in the object correctly according to my testing, *sigh*.
Gotta love global variables)

It then uses mailbox_cache_size_detail to calculate the ACTUAL record
length for this single cache item rather than blindly copying everything
up to the next index record's pointer.

Also note: in the event of cache corruption, mailbox_cache_size_detail
returns zero bytes, which correctly makes append_copy re-parse the
message file.  It's all shiny :)

Wes/Ken - please apply to CVS :)

Thanks,

Bron.
--
  Bron Gondwana
  brong@xxxxxxxxxxx

Going through my list of 2.3.13 patches to put together a local 2.3.14 build, I ran across this one. It doesn't appear to have made it into 2.3.14. Oversight, or is there something wrong with it?

Thanks.

-David

Index: cyrus-imapd-2.3.13/imap/index.c
===================================================================
--- cyrus-imapd-2.3.13.orig/imap/index.c	2008-12-07 23:51:36.000000000 +0000
+++ cyrus-imapd-2.3.13/imap/index.c	2008-12-08 01:51:28.000000000 +0000
@@ -3574,13 +3574,9 @@ void *rock;
 	/* Force copy and re-parse of message */
 	copyargs->copymsg[copyargs->nummsg].cache_len = 0;
     }
-    else if (msgno < (unsigned) imapd_exists) {
-	copyargs->copymsg[copyargs->nummsg].cache_len =
-	  CACHE_OFFSET(msgno+1) - CACHE_OFFSET(msgno);
-    }
     else {
 	copyargs->copymsg[copyargs->nummsg].cache_len =
-	  cache_end - CACHE_OFFSET(msgno);
+	  mailbox_cache_size_detail(copyargs->copymsg[copyargs->nummsg].cache_begin, cache_base, cache_end);
     }
     copyargs->copymsg[copyargs->nummsg].seen = seenflag[msgno];
     copyargs->copymsg[copyargs->nummsg].system_flags = SYSTEM_FLAGS(msgno);
Index: cyrus-imapd-2.3.13/imap/mailbox.c
===================================================================
--- cyrus-imapd-2.3.13.orig/imap/mailbox.c	2008-12-08 01:46:02.000000000 +0000
+++ cyrus-imapd-2.3.13/imap/mailbox.c	2008-12-08 02:04:34.000000000 +0000
@@ -301,8 +301,6 @@ unsigned long mailbox_cache_size(struct 
 {
     const char *p;
     unsigned long cache_offset;
-    unsigned int cache_ent;
-    const char *cacheitem, *cacheitembegin;
 
     assert((msgno > 0) && (msgno <= mailbox->exists));
 
@@ -310,22 +308,33 @@ unsigned long mailbox_cache_size(struct 
          ((msgno-1) * mailbox->record_size));
     
     cache_offset = ntohl(*((bit32 *)(p+OFFSET_CACHE_OFFSET)));
-    if (cache_offset > mailbox->cache_size) {
+
+    return mailbox_cache_size_detail(mailbox->cache_base + cache_offset,
+				     mailbox->cache_base,
+				     mailbox->cache_size);
+}
+
+unsigned long mailbox_cache_size_detail(const char *cache_item,
+                                        const char *cache_base,
+					unsigned long cache_size)
+{
+    unsigned int cache_ent;
+    const char *begin = cache_item;
+
+    if (begin < cache_base || begin >= cache_base + cache_size) {
+	/* already not in the area */
 	return 0;
     }
 
     /* Compute size of this record */
-    cacheitembegin = cacheitem = mailbox->cache_base + cache_offset;
-    if (cache_offset >= mailbox->cache_size)
-	return 0;
     for (cache_ent = 0; cache_ent < NUM_CACHE_FIELDS; cache_ent++) {
-	cacheitem = CACHE_ITEM_NEXT(cacheitem);
-	if (cacheitem < cacheitembegin ||
-	    cacheitem > cacheitembegin + mailbox->cache_size) {
+	cache_item = CACHE_ITEM_NEXT(cache_item);
+	if (cache_item < begin ||
+	    cache_item > cache_base + cache_size) {
 	    return 0; /* clearly bogus */
 	}
     }
-    return (cacheitem - cacheitembegin);
+    return (cache_item - begin);
 }
 
 /* function to be used for notification of mailbox changes/updates */
Index: cyrus-imapd-2.3.13/imap/mailbox.h
===================================================================
--- cyrus-imapd-2.3.13.orig/imap/mailbox.h	2008-12-08 01:51:37.000000000 +0000
+++ cyrus-imapd-2.3.13/imap/mailbox.h	2008-12-08 02:03:23.000000000 +0000
@@ -292,6 +292,9 @@ unsigned mailbox_cached_header(const cha
 unsigned mailbox_cached_header_inline(const char *text);
 
 unsigned long mailbox_cache_size(struct mailbox *mailbox, unsigned msgno);
+unsigned long mailbox_cache_size_detail(const char *cache_item, 
+					const char *cache_base, 
+					unsigned long cache_size);
 
 typedef unsigned mailbox_decideproc_t(struct mailbox *mailbox, void *rock,
 				      unsigned char *indexbuf,
----
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