iradization@gmail.com wrote:

Full_Name: Irad.k Version: recent from GitHub. OS: macOS URL: ftp://ftp.openldap.org/incoming/ Submission from: (NULL) (82.81.84.130)

Hi,

I'm working with LMDB with the following flags : MDB_NOMETASYNC | MDB_NOSUBDIR | MDB_NOTLS.

Somehow, even though the DB should be ACI(without the D), it got corrupted after recovering from kernel panic, and It crashes my process when trying to access one of the records (see crash log below).

Here's a link to the file :

https://drive.google.com/file/d/12Q3KYYrapiJOgiaccnDL3tQACkqrM3C5/view?usp=s...

This file is only 6 pages long, but the latest meta page claims that it's using 11 pages. Looking at the previous meta page, it claims that 9 pages were used.

Clearly your OS failed to write the complete contents out before it panicked. At the very least the file should have been 9 pages long. Sounds like you have an OS bug.

According to the crash log from the process, It can clearly be seen that the invalid address reside inside the mapped file region which is the lmdb mapped file, but still I get KERN_MEMORY_ERROR on that address.

...

From what I know, an attempt to access address within the mapped range can

either retrieve the page contents directly from memory (if it's already there), or trigger page fault trap that eventually lead to reading the missing data from disk and return it to process as well.

One thing that raise some concerns is that the file size is only 24k and the mapping spans over 256M. However, the file's meta data seems to be coherent to file contents.

Any idea how did it happen, and what exactly in the file cause this corruption ?

CRASH LOG :

Exception Type: EXC_BAD_ACCESS (SIGBUS) Exception Codes: KERN_MEMORY_ERROR at 0x000000010648800a Exception Note: EXC_CORPSE_NOTIFY

Termination Signal: Bus error: 10 Termination Reason: Namespace SIGNAL, Code 0xa Terminating Process: exc handler [0]

VM Regions Near 0x10648800a:

__LINKEDIT 0000000106464000-000000010647f000 [ 108K] r--/rwx SM=COW ^Z^C [/usr/lib/dyld] --> mapped file 000000010647f000-000000011647f000 [256.0M] r--/rwx SM=PRV Object_id=9034edd9 STACK GUARD 000070000f2b3000-000070000f2b4000 [ 4K] ---/rwx SM=NUL stack guard for thread 1

Thread 0 Crashed:: Dispatch queue: com.apple.main-thread 0 myprog 0x0000000101666756 mdb_page_search_root + 39 1 myprog 0x00000001016660f7 mdb_page_search + 182 2 myprog 0x00000001016614de mdb_cursor_set + 88 3 myprog 0x0000000101661476 mdb_get + 134