tree 4b2903a4b0a56dc30b445c29d7a0a97da986aafd
parent 16e87a2f3ebc26df27546fff469655628e7d48a9
author Petr Hosek <phosek@chromium.org> 1563825274 +0000
committer Petr Hosek <phosek@chromium.org> 1563825274 +0000

[libc++] Set __file_ to 0 in basic_filebuf::close() even if fclose fails

This issue was detected by ASan in one of our tests. This test manually
invokes basic_filebuf::cloe(). fclose(__h.release() returned a non-zero
exit status, so __file_ wasn't set to 0. Later when basic_filebuf
destructor ran, we would enter the if (__file_) block again leading to
heap-use-after-free error.

The POSIX specification for fclose says that independently of the return
value, fclose closes the underlying file descriptor and any further
access (including another call to fclose()) to the stream results in
undefined behavior. This is exactly what happened in our test case.

To avoid this issue, we have to always set __file_ to 0 independently of
the fclose return value.

Differential Revision: https://reviews.llvm.org/D64979

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@366730 91177308-0d34-0410-b5e6-96231b3b80d8