Hi all,
Is it possible to change the value of ASan's allocator_may_return_null at runtime or somehow disable this check temporarily? If I install an LLVM bad_alloc_error_handler, ASan's allocator wrapper detects this first and terminates the process instead of returning 0, preventing the custom handler from being called.
Thanks,
Jonas
Hi all,
Is it possible to change the value of ASan's allocator_may_return_null at
runtime or somehow disable this check temporarily? If I install an LLVM
bad_alloc_error_handler, ASan's allocator wrapper detects this first and
terminates the process instead of returning 0, preventing the custom
handler from being called.
Is this question related to "r312582 - Revert "[Decompression] Fail
gracefully when out of memory""?
It is! Though even if we don’t need it, I’d still be interested to know whether this is possible. If the answer is no, I wonder how useful error handler is (which isn’t currently used, at least not upstream).
Hi all,
Is it possible to change the value of ASan's allocator_may_return_null at
runtime or somehow disable this check temporarily? If I install an LLVM
bad_alloc_error_handler, ASan's allocator wrapper detects this first and
terminates the process instead of returning 0, preventing the custom
handler from being called.Is this question related to "r312582 - Revert "[Decompression] Fail
gracefully when out of memory”"?It is! Though even if we don't need it, I’d still be interested to know
whether this is possible.
I'm not sure what you are asking for, exactly.
Here is how it works:
% clang++ -fsanitize=address
~/llvm/projects/compiler-rt/test/asan/TestCases/allocator_returns_null.cc
% ./a.out malloc
==2503==WARNING: AddressSanitizer failed to allocate 0x10000000001 bytes
==2503==AddressSanitizer's allocator is terminating the process instead of
returning 0
==2503==If you don't like this behavior set allocator_may_return_null=1
% ASAN_OPTIONS=allocator_may_return_null=1 ./a.out malloc
==2513==WARNING: AddressSanitizer failed to allocate 0x10000000001 bytes
errno: 12
x: 0
So you can change the value of allocator_may_return_null at startup.
There is no way to change this while the process is running.
You can set allocator_may_return_null per binary
using __asan_default_options
(see llvm/projects/compiler-rt/include/sanitizer/asan_interface.h)
but unless absolutely necessary I'd try to avoid this. Lots of things may
go wrong.
If the answer is no, I wonder how useful error handler is (which isn't
currently used, at least not upstream).
Imho, an error handler that tries to recover from OOM is a very dangerous
thing and should be avoided.
This essentially introduces a very fragile code to the least tests path.
--kcc
I considered doing that for my test case, but fuzzing (with ASan) would still trigger a crash.
That answers my question, thanks!
I totally agree, and in that respect it’s probably a good thing that it can’t be disabled at run time.