[Date Prev][Date Next]
(ITS#8898) mdb_get on corrupted LMDB file crash the process
Version: recent from GitHub.
Submission from: (NULL) (18.104.22.168)
I'm working with LMDB with the following flags : MDB_NOMETASYNC | MDB_NOSUBDIR
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 :
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
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 
VM Regions Near 0x10648800a:
__LINKEDIT 0000000106464000-000000010647f000 [ 108K] r--/rwx SM=COW
--> mapped file 000000010647f000-000000011647f000 [256.0M] r--/rwx
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