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[lsan] fix a rare lsan false positive: ensure that we don't re-sort the chunks_ array while iterating over it. A test is hard to create, but I've added a consistency check that fires w/o the fix on existing tests. The bug analysis and the initial patch were provided by Pierre Bourdon 

llvm-svn: 286478
This commit is contained in:
Kostya Serebryany 2016-11-10 17:27:28 +00:00
parent e517f0a417
commit 56cec3d662
1 changed files with 19 additions and 12 deletions
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31
compiler-rt/lib/sanitizer_common/sanitizer_allocator_secondary.h
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@ -161,6 +161,14 @@ class LargeMmapAllocator {
return GetUser(h);
}
void EnsureSortedChunks() {
if (chunks_sorted_) return;
SortArray(reinterpret_cast<uptr*>(chunks_), n_chunks_);
for (uptr i = 0; i < n_chunks_; i++)
chunks_[i]->chunk_idx = i;
chunks_sorted_ = true;
}
// This function does the same as GetBlockBegin, but is much faster.
// Must be called with the allocator locked.
void *GetBlockBeginFastLocked(void *ptr) {
@ -168,16 +176,10 @@ class LargeMmapAllocator {
uptr p = reinterpret_cast<uptr>(ptr);
uptr n = n_chunks_;
if (!n) return nullptr;
if (!chunks_sorted_) {
// Do one-time sort. chunks_sorted_ is reset in Allocate/Deallocate.
SortArray(reinterpret_cast<uptr*>(chunks_), n);
for (uptr i = 0; i < n; i++)
chunks_[i]->chunk_idx = i;
chunks_sorted_ = true;
min_mmap_ = reinterpret_cast<uptr>(chunks_[0]);
max_mmap_ = reinterpret_cast<uptr>(chunks_[n - 1]) +
chunks_[n - 1]->map_size;
}
EnsureSortedChunks();
auto min_mmap_ = reinterpret_cast<uptr>(chunks_[0]);
auto max_mmap_ =
reinterpret_cast<uptr>(chunks_[n - 1]) + chunks_[n - 1]->map_size;
if (p < min_mmap_ || p >= max_mmap_)
return nullptr;
uptr beg = 0, end = n - 1;
@ -230,8 +232,14 @@ class LargeMmapAllocator {
// Iterate over all existing chunks.
// The allocator must be locked when calling this function.
void ForEachChunk(ForEachChunkCallback callback, void *arg) {
for (uptr i = 0; i < n_chunks_; i++)
EnsureSortedChunks(); // Avoid doing the sort while iterating.
for (uptr i = 0; i < n_chunks_; i++) {
auto t = chunks_[i];
callback(reinterpret_cast<uptr>(GetUser(chunks_[i])), arg);
// Consistency check: verify that the array did not change.
CHECK_EQ(chunks_[i], t);
CHECK_EQ(chunks_[i]->chunk_idx, i);
}
}
private:
@ -263,7 +271,6 @@ class LargeMmapAllocator {
uptr page_size_;
Header *chunks_[kMaxNumChunks];
uptr n_chunks_;
uptr min_mmap_, max_mmap_;
bool chunks_sorted_;
struct Stats {
uptr n_allocs, n_frees, currently_allocated, max_allocated, by_size_log[64];