r/w access to fd from creat()

[Guy Harris]

> It has been my experience that the file descriptor returned from a
> successful invocation of creat() is writaable but not readable, regardless
> of the mode specified to creat().
> 
> Does anybody know of a way to change this (kernel mods are unacceptable)?

There isn't any which doesn't involve changing the kernel, except for
closing and reopening the file (which won't work in your case).

> One problem is that I occasionally need r/w access to a creat()ed fd which
> must have a mode of 0444 for exclusive lock purposes.

Try using "link" and "unlink" to/from a file for locking purposes; it means
the file doesn't have to be unwritable, and also means you can lock out the
superuser.

	Guy Harris