On Mon, Sep 29, 2008 at 12:37:12PM +0100, Mark Cave-Ayland wrote:
> Hi there,
>
> I'm experiencing a problem with Cyrus 2.3.8 interacting with an Outlook
> client and was hoping this would be the right place to get some advice.
>
> What happens is that periodically (maybe around once a month?) we have
> one particular user who contacts us complaining that they are unable
> access their mailbox. Generally we always find the same thing: there is
> an imapd process accessing his seen DB which is running at 100% CPU.
> Once this process is killed then things go back to normal and the user
> can log in.
>
> The latest report we had of this problem happening again was this
> morning, and fortunately I was in a position to attack it with gdb and a
> file of debug symbols. This showed that the process in question was
> getting stuck in a loop in index_expungeuidlist(). I've uploaded the
> transcript of my gdb session to
> http://pastebin.siriusit.co.uk/cyrus-imapd-gdb.txt for people who are
> familiar with cyrus internals.
>
> The short story appears to be that newseenuids (new) points to an empty
> string ('\0') and so the code gets stuck because of the following at
> line 532 of imap/index.c in index_checkseen():
>
> oldseen = (*old == ':');
oldseen = 0;
> Since *old is an empty string, oldseen will always be 0, and so the
> while() loop never exits. Unfortunately this is the first time I've ever
> looked at cyrus internals, so am not really sure what the seen list
> should look like normally.
No, BUT.
while (oldnext <= uid) {
...
if (!*old) oldnext = mailbox->last_uid+1;
}
if your mailbox is corrupted such that last_uid is less than
an actual uid in the mailbox, then you will get an infinite
loop here.
> The confusing thing is that we have been using these packages for
> several clients and this is the *only* particular server and the *only*
> user on this server experiencing this problem. The one thing we have
> noticed is that this particular user has a larger mailbox compared to
> the other users (~1GB) but then it doesn't seem so large as if it would
> cause any problems.
Yeah, it's a corrupted mailbox.
> Finally, one more thing to add is that we have already gone through the
> steps of rebuilding the seen DB skiplist using the skiplist.py script
> several times when this has happened in the past, and it has made no
> difference.
No, it won't. You need to fix the mailbox or patch the code to not be
put into an infinite loop by a bogus index file.
The attached patch might do the trick for you. I just slapped it
together on spec. It compiles, that's about all I can offer about
it :)
Bron ( and no, I can't spell. Tough ;) )
Index: cyrus-imapd-2.3.12p2/imap/index.c
===================================================================
--- cyrus-imapd-2.3.12p2.orig/imap/index.c 2008-09-29 22:31:30.000000000 +1000
+++ cyrus-imapd-2.3.12p2/imap/index.c 2008-09-29 22:36:38.000000000 +1000
@@ -584,7 +584,12 @@
else {
oldseen = (*old == ':');
oldnext = 0;
- if (!*old) oldnext = mailbox->last_uid+1;
+ if (!*old) {
+ oldnext = mailbox->last_uid+1;
+ /* just in case the index is corrupted, don't
+ * loop forever */
+ if (oldnext < uid) oldnext = uid;
+ }
else old++;
while (cyrus_isdigit((int) *old)) {
oldnext = oldnext * 10 + *old++ - '0';
@@ -602,6 +607,9 @@
newnext = 0;
if (!*new) {
newnext = mailbox->last_uid+1;
+ /* just in case the index is corrupted, don't
+ * loop forever */
+ if (newnext < uid) newnext = uid;
neweof++;
}
else new++;
----
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