[Bug libstdc++/104161] Potential Security Vulnerability: remove_all and symbolic link

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104161

--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jonathan Wakely <redi@gcc.gnu.org>:

https://gcc.gnu.org/g:5750952bec1e632d1f804f4a1bed2f74c0f3b189

commit r12-7099-g5750952bec1e632d1f804f4a1bed2f74c0f3b189
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Feb 7 23:36:47 2022 +0000

    libstdc++: Fix filesystem::remove_all for Windows [PR104161]

    The recursive_directory_iterator::__erase member was failing for
    Windows, because the entry._M_type value is always file_type::none
    (because _Dir_base::advance doesn't populate it for Windows) and
    top.unlink uses fs::remove which sets an error using the
    system_category. That meant that ec.value() was a Windows error code and
    not an errno value, so the comparisons to EPERM and EISDIR failed.
    Instead of depending on a specific Windows error code for attempting to
    remove a directory, just use directory_entry::refresh() to query the
    type first. This doesn't avoid the TOCTTOU races with directory
    symlinks, but we can't avoid them on Windows without openat and
    unlinkat, and creating symlinks requires admin privs on Windows anyway.

    This also fixes the fs::remove_all(const path&) overload, which was
    supposed to use the same logic as the other overload, but I forgot to
    change it before my previous commit.

    libstdc++-v3/ChangeLog:

            PR libstdc++/104161
            * src/c++17/fs_dir.cc (fs::recursive_directory_iterator::__erase):
            [i_GLIBCXX_FILESYSTEM_IS_WINDOWS]: Refresh entry._M_type member,
            instead of checking for errno values indicating a directory.
            * src/c++17/fs_ops.cc (fs::remove_all(const path&)): Use similar
            logic to non-throwing overload.
            (fs::remove_all(const path&, error_code&)): Add comments.
            * src/filesystem/ops-common.h: Likewise.