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| author | Nirbhay Choubey <nirbhay.choubey@oracle.com> | 2011-11-29 17:59:35 +0530 |
|---|---|---|
| committer | Nirbhay Choubey <nirbhay.choubey@oracle.com> | 2011-11-29 17:59:35 +0530 |
| commit | c67a91f11afd730ab050e3c5da16411b95c325a7 (patch) | |
| tree | 370462b6c1d10f330b9628f9b4ea81cfd8f607eb /storage/myisam | |
| parent | a00f87bf155fda703ffd314e5d8166583db92d93 (diff) | |
| download | mariadb-git-c67a91f11afd730ab050e3c5da16411b95c325a7.tar.gz | |
Bug#11756764 48726: MYSQLD KEEPS CRASHING WITH SIGSEGV
WITH MYISAM_USE_MMAP ENABLED
MySQL server can crash due to segmentation fault when
started with myisam_use_mmap.
The reason behind this being, while making a request to
unmap (munmap) the previously mapped memory (mmap), the
size passed was 7 bytes larger than the size requested at
the time of mapping. This can eventually unmap the adjacent
memory mapped block, belonging to some other memory-map pool.
Hence the subsequent call to mmap can map a region which was
still a valid memory mapped area.
Fixed by removing the extra 7-byte margin which was erroneously
added to the size, used for unmappping.
storage/myisam/mi_close.c:
Bug#11756764 48726: MYSQLD KEEPS CRASHING WITH SIGSEGV
WITH MYISAM_USE_MMAP ENABLED
Added a condition to call _mi_unmap_file() in case
of compressed records. mi_munmap_file() is called
otherwise.
storage/myisam/mi_packrec.c:
Bug#11756764 48726: MYSQLD KEEPS CRASHING WITH SIGSEGV
WITH MYISAM_USE_MMAP ENABLED
mi_dynmap_file() function, after successfully executing
mmap, stores the total size in info->s->mapped_length
variable. Now, if mi_dynmap_file() is invoked with a size
with an extra 7-byte margin (MEMMAP_EXTRA_MARGIN),
the margin will eventually also get stored in mapped_length.
So, un-mapping function can simply use the value stored in
mapped_length in order to unmap the previously mapped
region.
Diffstat (limited to 'storage/myisam')
| -rw-r--r-- | storage/myisam/mi_close.c | 7 | ||||
| -rw-r--r-- | storage/myisam/mi_packrec.c | 7 |
2 files changed, 10 insertions, 4 deletions
diff --git a/storage/myisam/mi_close.c b/storage/myisam/mi_close.c index bb95aff24d7..a6911814608 100644 --- a/storage/myisam/mi_close.c +++ b/storage/myisam/mi_close.c @@ -87,7 +87,12 @@ int mi_close(register MI_INFO *info) } #ifdef HAVE_MMAP if (share->file_map) - _mi_unmap_file(info); + { + if (share->options & HA_OPTION_COMPRESS_RECORD) + _mi_unmap_file(info); + else + mi_munmap_file(info); + } #endif if (share->decode_trees) { diff --git a/storage/myisam/mi_packrec.c b/storage/myisam/mi_packrec.c index e6ad4c3defc..005f8c65d71 100644 --- a/storage/myisam/mi_packrec.c +++ b/storage/myisam/mi_packrec.c @@ -1553,13 +1553,14 @@ my_bool _mi_memmap_file(MI_INFO *info) void _mi_unmap_file(MI_INFO *info) { - VOID(my_munmap((char*) info->s->file_map, - (size_t) info->s->mmaped_length + MEMMAP_EXTRA_MARGIN)); + DBUG_ASSERT(info->s->options & HA_OPTION_COMPRESS_RECORD); + + VOID(my_munmap((char*) info->s->file_map, (size_t) info->s->mmaped_length)); if (myisam_mmap_size != SIZE_T_MAX) { pthread_mutex_lock(&THR_LOCK_myisam_mmap); - myisam_mmap_used-= info->s->mmaped_length + MEMMAP_EXTRA_MARGIN; + myisam_mmap_used-= info->s->mmaped_length; pthread_mutex_unlock(&THR_LOCK_myisam_mmap); } } |