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map_backing_store() did not acquire a cache ref in case it created a private

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mapping, but it connected the vm_cache objects, so if it failed later, and
thus called vm_cache_release_ref() the object could have been freed accidently.
Most uses of map_backing_store() explicetly acquired a cache_ref *after* the
call was successful, but _vm_map_file() did not do this.
_vm_map_file() might still not work correctly, though, need to have a closer
look at it.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@17692 a95241bf-73f2-0310-859d-f6bbb57e9c96
This commit is contained in:
Axel Dörfler 2006-06-01 18:14:59 +00:00
parent bbb7119577
commit a9fa017d82
1 changed files with 12 additions and 2 deletions
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14
src/system/kernel/vm/vm.cpp
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@ -553,6 +553,7 @@ map_backing_store(vm_address_space *addressSpace, vm_store *store, void **_virtu
newCache->scan_skip = cache->scan_skip;
newCache->source = cache;
vm_cache_acquire_ref(cacheRef);
cache = newCache;
cacheRef = cache->ref;
@ -1271,8 +1272,13 @@ vm_clone_area(team_id team, const char *name, void **address, uint32 addressSpec
address, sourceArea->cache_offset, sourceArea->size, addressSpec,
sourceArea->wiring, protection, mapping, &newArea, name);
}
if (status == B_OK)
if (status == B_OK && mapping != REGION_PRIVATE_MAP) {
// If the mapping is REGION_PRIVATE_MAP, map_backing_store() needed
// to create a new ref, and has therefore already acquired a reference
// to the source cache - but otherwise it has no idea that we need
// one.
vm_cache_acquire_ref(sourceArea->cache_ref);
}
vm_put_area(sourceArea);
vm_put_address_space(addressSpace);
@ -1540,7 +1546,11 @@ vm_copy_area(team_id addressSpaceID, const char *name, void **_address, uint32 a
if (status < B_OK)
goto err;
vm_cache_acquire_ref(cacheRef);
if (!writableCopy) {
// map_backing_store() cannot know it has to acquire a ref to
// the store for REGION_NO_PRIVATE_MAP
vm_cache_acquire_ref(cacheRef);
}
// If the source area is writable, we need to move it one layer up as well