Re: [PATCH v2 RESEND] posix_acl: Clear SGID bit when setting file permissions

[Eric Biggers <ebiggers@google.com>]

On Mon, Sep 19, 2016 at 05:42:48PM +0200, Jan Kara wrote:
> When file permissions are modified via chmod(2) and the user is not in
> the owning group or capable of CAP_FSETID, the setgid bit is cleared in
> inode_change_ok().  Setting a POSIX ACL via setxattr(2) sets the file
> permissions as well as the new ACL, but doesn't clear the setgid bit in
> a similar way; this allows to bypass the check in chmod(2).  Fix that.
> 

Hi Jan,

This patch is causing xfstests generic/314 to fail.  This test is supposed to
test "SGID inheritance on subdirectories", and the failure is because subdir2
unexpectedly ends up without a SGID bit.  This happens because the following
commands now result in the SGID bit on the parent directory "$TEST_DIR/$seq-dir"
being cleared rather than set:

	mkdir $TEST_DIR/$seq-dir
	chown $qa_user:12345 $TEST_DIR/$seq-dir
	chmod 2775 $TEST_DIR/$seq-dir
	su $qa_user -c "setfacl -m u:$qa_user:rwx,d:u:$qa_user:rwx $TEST_DIR/$seq-dir"

Is this the expected behavior now?

Thanks,

Eric