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[PATCH v2 0/3] Support opening a symlink with O_PATH | O_NOFOLLOW
- From: Ken Brown <kbrown at cornell dot edu>
- To: "cygwin-patches at cygwin dot com" <cygwin-patches at cygwin dot com>
- Date: Sun, 29 Dec 2019 17:56:55 +0000
- Subject: [PATCH v2 0/3] Support opening a symlink with O_PATH | O_NOFOLLOW
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Currently, opening a symlink with O_NOFOLLOW fails with ELOOP.
Following Linux, the first patch in this series allows the call to
succeed if O_PATH is also specified.
According to the Linux man page for 'open', the file descriptor
returned by the call should be usable as the dirfd argument in calls
to fstatat and readlinkat with an empty pathname, to have
the calls operate on the symbolic link. The second and third patches
achieve this. For fstatat, we do this by adding support
for the AT_EMPTY_PATH flag.
Note: The man page mentions fchownat and linkat also. linkat already
supports the AT_EMPTY_PATH flag, so nothing needs to be done. But I
don't understand how this could work for fchownat, because fchown
fails with EBADF if its fd argument was opened with O_PATH. So I
haven't touched fchownat.
Am I missing something?
Ken Brown (3):
Cygwin: allow opening a symlink with O_PATH | O_NOFOLLOW
Cygwin: readlinkat: allow pathname to be empty
Cygwin: fstatat: support the AT_EMPTY_PATH flag
winsup/cygwin/syscalls.cc | 40 +++++++++++++++++++++++++++++++++------
1 file changed, 34 insertions(+), 6 deletions(-)
--
2.21.0