[Dovecot] Memory leak by getting the virtual size of a IMAP folder

[Dafan Zhai]

Hi everyone,

I am writing a dovecot statistic plugin, which calls the 
'mailbox_get_metadata' function with MAILBOX_METADATA_VIRTUAL_SIZE as 
the 2nd parameter.

enum mailbox_status_items metadata_items = MAILBOX_METADATA_VIRTUAL_SIZE;
struct mailbox_metadata metadata;
mailbox_get_metadata(mailbox, metadata_items, &metadata);

but Valgrind finds a memory leak when this function is called:
---------------------------------------------------snip--------------------------------------------------------------
==10304== 12,288 bytes in 3 blocks are definitely lost in loss record 74 
of 76
==10304==    at 0x40222A4: calloc (in 
/usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==10304==    by 0x416EE9F: block_alloc (mempool-alloconly.c:237)
==10304==    by 0x416F16C: pool_alloconly_create (mempool-alloconly.c:140)
==10304==    by 0x409C07D: mail_search_build_init (mail-search-build.c:187)
==10304==    by 0x40C77F1: index_mailbox_get_metadata (index-status.c:200)
==10304==    by 0x4067102: maildir_mailbox_get_metadata 
(maildir-storage.c:486)
==10304==    by 0x409F78B: mailbox_get_metadata (mail-storage.c:1298)
==10304==    by 0x490492D: mailbox_status_update (statistic-plugin.c:310)
==10304==    by 0x4904E2E: statistic_mail_save (statistic-plugin.c:426)
==10304==    by 0x41A054D: notify_contexts_mail_save (notify-plugin.c:61)
==10304==    by 0x41A104F: notify_save_finish (notify-storage.c:143)
==10304==    by 0x409EE94: mailbox_save_finish (mail-storage.c:1673)
---------------------------------------------------snip--------------------------------------------------------------

I have looked into the source code, and found that  from the 
'mail_search_build_init' function call in 
lib-storage/index/index-status.c:200 a pool is created, but the pool is 
not freed in the mailbox_search_deinit function call in 
lib-storage/index/index-status.c:218.
This may be the reason of the memory leak. But I do not know how to free 
the pool.

It seems to me that doveadm is having the same memory leak because it is 
using 'mail_search_build_init' too.
---------------------------------------------------snip--------------------------------------------------------------
# valgrind --leak-check=full doveadm mailbox status -u testuser1 vsize INBOX
==10457== Memcheck, a memory error detector
==10457== Copyright (C) 2002-2010, and GNU GPL'd, by Julian Seward et al.
==10457== Using Valgrind-3.6.1 and LibVEX; rerun with -h for copyright info
==10457== Command: doveadm mailbox status -u testuser1 vsize INBOX
==10457==
INBOX vsize=41643319
==10457==
==10457== HEAP SUMMARY:
==10457== in use at exit: 4,356 bytes in 3 blocks
==10457== total heap usage: 440 allocs, 437 frees, 539,124 bytes allocated
==10457==
==10457== 4,096 bytes in 1 blocks are definitely lost in loss record 3 of 3
==10457== at 0x40222A4: calloc (in 
/usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==10457== by 0x41AEE9F: ??? (in /usr/lib/dovecot/libdovecot.so.0.0.0)
==10457== by 0x41AF16C: pool_alloconly_create (in 
/usr/lib/dovecot/libdovecot.so.0.0.0)
==10457== by 0x40DC07D: mail_search_build_init (in 
/usr/lib/dovecot/libdovecot-storage.so.0.0.0)
==10457== by 0x8057EB8: doveadm_mail_mailbox_search_args_build (in 
/usr/bin/doveadm)
==10457== by 0x805855A: ??? (in /usr/bin/doveadm)
==10457== by 0x8053A7B: doveadm_mail_single_user (in /usr/bin/doveadm)
==10457== by 0x8053D2B: ??? (in /usr/bin/doveadm)
==10457== by 0x80541CF: doveadm_mail_try_run (in /usr/bin/doveadm)
==10457== by 0x805B863: main (in /usr/bin/doveadm)
==10457==
==10457== LEAK SUMMARY:
==10457== definitely lost: 4,096 bytes in 1 blocks
==10457== indirectly lost: 0 bytes in 0 blocks
==10457== possibly lost: 0 bytes in 0 blocks
==10457== still reachable: 260 bytes in 2 blocks
==10457== suppressed: 0 bytes in 0 blocks
==10457== Reachable blocks (those to which a pointer was found) are not 
shown.
==10457== To see them, rerun with: --leak-check=full --show-reachable=yes
==10457==
==10457== For counts of detected and suppressed errors, rerun with: -v
==10457== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 122 from 35)
---------------------------------------------------snip--------------------------------------------------------------

Dovecot version: 2.1.9
OS: Linux 3.0.30-dist i686
maildir:~/Maildir:LAYOUT=fs:INBOX=~/Maildir/INBOX

I have applied the following patches from the dovecot 2.1 branch fixing 
memory leaks:
http://hg.dovecot.org/dovecot-2.1/rev/7bdbca7b0913
http://hg.dovecot.org/dovecot-2.1/rev/963482677c0b


It would be nice if you could give me some hints how I can address this 
issue?

Thanks in advance!

Greetings,
Dafan