ART: Fix memory unmapped twice issue in ElfFile::Load(bool)
Root Cause:
The overlapped memory region will be unmapped by
(1) ~MemMap() of reservation MemMap (reserve) and
(2) ~MemMap() of "reuse" MemMap (segment).
Someone takes the memory region after (1) and it will be unmapped in (2).
So, SIGSEGV occurs when using the unmapped memory region.
Solution:
Fixes this issue by skip unmap "reuse" MemMap in destructor.
And always create reservation MemMap before "reuse" MemMap. (It also solved
the fixupELF case which does not reserve the whole needed memory region).
Bug: 16486685
Change-Id: I8f2538861d5c3fa7b9a04d2c3f516319cc060291
diff --git a/runtime/mem_map.h b/runtime/mem_map.h
index defa6a5..872c63b 100644
--- a/runtime/mem_map.h
+++ b/runtime/mem_map.h
@@ -73,7 +73,9 @@
// Map part of a file, taking care of non-page aligned offsets. The
// "start" offset is absolute, not relative. This version allows
- // requesting a specific address for the base of the mapping.
+ // requesting a specific address for the base of the
+ // mapping. "reuse" allows us to create a view into an existing
+ // mapping where we do not take ownership of the memory.
//
// On success, returns returns a MemMap instance. On failure, returns a NULL;
static MemMap* MapFileAtAddress(byte* addr, size_t byte_count, int prot, int flags, int fd,
@@ -134,7 +136,7 @@
private:
MemMap(const std::string& name, byte* begin, size_t size, void* base_begin, size_t base_size,
- int prot) LOCKS_EXCLUDED(Locks::mem_maps_lock_);
+ int prot, bool reuse) LOCKS_EXCLUDED(Locks::mem_maps_lock_);
static void DumpMaps(std::ostream& os, const std::multimap<void*, MemMap*>& mem_maps)
LOCKS_EXCLUDED(Locks::mem_maps_lock_);
@@ -145,7 +147,7 @@
static MemMap* GetLargestMemMapAt(void* address)
EXCLUSIVE_LOCKS_REQUIRED(Locks::mem_maps_lock_);
- std::string name_;
+ const std::string name_;
byte* const begin_; // Start of data.
size_t size_; // Length of data.
@@ -153,6 +155,11 @@
size_t base_size_; // Length of mapping. May be changed by RemapAtEnd (ie Zygote).
int prot_; // Protection of the map.
+ // When reuse_ is true, this is just a view of an existing mapping
+ // and we do not take ownership and are not responsible for
+ // unmapping.
+ const bool reuse_;
+
#if USE_ART_LOW_4G_ALLOCATOR
static uintptr_t next_mem_pos_; // Next memory location to check for low_4g extent.
#endif