[compiler-rt] fcf92cb - [tsan] Check for nullptr on user_alloc_usable_size_fast

[Jin Xin Ng via llvm-commits]

Author: Jin Xin Ng
Date: 2023-06-13T00:00:31Z
New Revision: fcf92cb8008d802de4b64ae765fed1ffe3871a97

URL: https://github.com/llvm/llvm-project/commit/fcf92cb8008d802de4b64ae765fed1ffe3871a97
DIFF: https://github.com/llvm/llvm-project/commit/fcf92cb8008d802de4b64ae765fed1ffe3871a97.diff

LOG: [tsan] Check for nullptr on user_alloc_usable_size_fast

MBlock could be null (in the context of a call from RunFreeHooks)
if a static object was runtime initialized before tsan finished
initializing and that object later did a free().

While having the check isn't strictly required by
__sanitizer_get_allocated_size_fast's contract, a user's static object
would expect ptrs returned from malloc to be valid inputs.

Differential Revision: https://reviews.llvm.org/D152755

Added: 
    

Modified: 
    compiler-rt/lib/tsan/rtl/tsan_mman.cpp

Removed: 
    


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diff  --git a/compiler-rt/lib/tsan/rtl/tsan_mman.cpp b/compiler-rt/lib/tsan/rtl/tsan_mman.cpp
index ac6d005fc1c05..7b9dc81a3f6c3 100644
--- a/compiler-rt/lib/tsan/rtl/tsan_mman.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_mman.cpp
@@ -379,6 +379,10 @@ uptr user_alloc_usable_size(const void *p) {
 
 uptr user_alloc_usable_size_fast(const void *p) {
   MBlock *b = ctx->metamap.GetBlock((uptr)p);
+  // Static objects may have malloc'd before tsan completes
+  // initialization, and may believe returned ptrs to be valid.
+  if (!b)
+    return 0;  // Not a valid pointer.
   if (b->siz == 0)
     return 1;  // Zero-sized allocations are actually 1 byte.
   return b->siz;