[Bug 50283] New: FILE_OPEN_REPARSE_POINT breaks error reporting for deletes of directories

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=50283

Bug ID: 50283
           Summary: FILE_OPEN_REPARSE_POINT breaks error reporting for
                    deletes of directories
           Product: Wine-staging
           Version: unspecified
          Hardware: x86-64
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: -unknown
          Assignee: [e-mail]
          Reporter: [e-mail]
                CC: [e-mail], [e-mail],
                    [e-mail]
      Distribution: ---

Created attachment 68840
  --> https://bugs.winehq.org/attachment.cgi?id=68840
Test program

In order to generically delete a file system entry, regardless of whether it is
a regular file, symlink or directory, one can open a handle to it and delete it
with a call to SetFileInformationByHandle(FileDispositionInfo). By opening the
handle with FILE_FLAG_OPEN_REPARSE_POINT, a potential symlink gets handled by
removing the symlink itself, not the target file it points to.

If a handle opened with the FILE_FLAG_OPEN_REPARSE_POINT flag set turns out to
be a directory, error reporting for the SetFileInformationByHandle call fails.
This is caused by [1] in combination with [2]. These two cases make O_SYMLINK,
which includes O_PATH, be added when opening the file descriptor which turns
out to be a directory. The O_PATH flag causes the later fdopendir() and
readdir() to not return anything, causing is_dir_empty [3] to indicate that the
directory is empty and removal will succeed, even though it doesn't.

This triggers errors in a std::filesystem testcase in libc++ [4], when checking
to make sure that attempts to remove a non-empty directory properly signals
errors.

[1]
https://github.com/wine-staging/wine-staging/blob/fce121fcd95380ca56c9d027be...
[2]
https://github.com/wine-staging/wine-staging/blob/fce121fcd95380ca56c9d027be...
[3]
https://source.winehq.org/git/wine.git/blob/fac1e40aaf0726a3e328a922cb496927...
[4]
https://github.com/llvm/llvm-project/blob/1e260f955d3123351fc68de8c2dde02b1b...

The issue can be reproduced with the attached fairly minimal test program.

[Bug 50283] FILE_OPEN_REPARSE_POINT breaks error reporting for deletes of directories

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=50283

--- Comment #1 from Erich E. Hoover  ---
It took me a while this weekend to figure out a way "around" this problem, but
the solution I came up with is really interesting:
===
    dir_fd = openat( fd, ".", O_RDONLY | O_DIRECTORY | O_NONBLOCK );
    if (dir_fd == -1)
        return -1;
    if (!(dir = fdopendir( dir_fd )))
    ...
    closedir( dir );
    close( dir_fd );
===
Essentially, we can "recreate" the fd with new permissions using openat() so
that it has the correct access rights for fdopendir().  This may be very useful
for implementing some other features...

Anyway, if you don't mind checking, this issue should now be fixed by staging
commit cfe1b94e0f53219cf292fea9b4618d909c282fbf.

[Bug 50283] FILE_OPEN_REPARSE_POINT breaks error reporting for deletes of directories

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=50283

Martin Storsjö  changed:

What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |FIXED

--- Comment #2 from Martin Storsjö  ---
This one also seems to be working as it should now, thanks!

[Bug 50283] FILE_OPEN_REPARSE_POINT breaks error reporting for deletes of directories

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=50283

Erich E. Hoover  changed:

What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |CLOSED

--- Comment #3 from Erich E. Hoover  ---
Fixed in wine-staging 6.2.