[PATCH 0/3] Fix the O_PATH support for FIFOs
Corinna Vinschen
corinna-cygwin@cygwin.com
Fri Jan 24 10:29:00 GMT 2020
On Jan 23 16:31, Ken Brown wrote:
> Commit aa55d22c, "Cygwin: honor the O_PATH flag when opening a FIFO",
> fixed a hang but otherwise didn't accomplish the purpose of the O_PATH
> flag as stated in the Linux man page for open(2):
>
> Obtain a file descriptor that can be used for two purposes: to
> indicate a location in the filesystem tree and to perform
> operations that act purely at the file descriptor level. The
> file itself is not opened, and other file operations (e.g.,
> read(2), write(2), fchmod(2), fchown(2), fgetxattr(2),
> ioctl(2), mmap(2)) fail with the error EBADF.
>
> [The man page goes on to describe operations that *can* be
> performed: close(2), fchdir(2), fstat(2),....]
>
> Opening a file or directory with the O_PATH flag requires no
> permissions on the object itself (but does require execute
> permission on the directories in the path prefix).
>
> The first problem in the current implementation is that if open(2) is
> called on a FIFO, fhandler_base::device_access_denied is called and
> tries to open the FIFO with read access, which isn't supposed to be
> required. This is fixed by the first patch in this series.
>
> The second patch makes fhandler_fifo::open call fhandler_base::open_fs
> if O_PATH is set, so that we actually obtain a handle that can be used
> for the purposes stated above.
>
> The third page tweaks fhandler_fifo::fcntl and fhandler_fifo::dup so
> that they work with O_PATH.
>
> In a followup email I'll provide the program I used to test this
> implementation.
>
> Ken Brown (3):
> Cygwin: device_access_denied: return false if O_PATH is set
> Cygwin: re-implement fhandler_fifo::open with O_PATH
> Cygwin: FIFO: tweak fcntl and dup when O_PATH is set
>
> winsup/cygwin/fhandler.cc | 3 +++
> winsup/cygwin/fhandler_fifo.cc | 15 ++++++---------
> 2 files changed, 9 insertions(+), 9 deletions(-)
>
> --
> 2.21.0
Pushed. I'll create new developer snapshots.
Thanks,
Corinna
--
Corinna Vinschen
Cygwin Maintainer
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: not available
URL: <http://cygwin.com/pipermail/cygwin-patches/attachments/20200124/c694c03b/attachment.sig>
More information about the Cygwin-patches
mailing list