On Fri, 2003-10-31 at 12:02, M. Warner Losh wrote: > In message: <[EMAIL PROTECTED]> > andi payn <[EMAIL PROTECTED]> writes: > : On Fri, 2003-10-31 at 08:27, David Malone wrote: > : > On Thu, Oct 30, 2003 at 07:46:38AM -0800, andi payn wrote: > : > > In FreeBSD, this doesn't work; you just get EINVAL. > : > > : > I believe this is because of a security problem discovered a few > : > years ago, where you could open a file like /dev/io for neither > : > read nor write but still get the special privelages associated with > : > having the file open. > : > > : > If you were to allow people to open files without read or write > : > permission you'd need to fix problems like this in a different way. > : > : It seems to me that the right way to fix this is to ensure that only the > : superuser can open /dev/io device, no matter what permissions are on it. > > This might not be a bad idea, but it would force at least one company > (mine) to rewrite at least some of their software to run as root. we > currently don't run some things as root because we don't trust them. > But then you are getting into special case kludges. Better to require > that it is opened read or write permissions.
Well, the io(4) manpage says: > In addition to any file access permissions on /dev/io, the kernel > enforces that only the super-user may open this device. If this is not true--and especially if it's not true by design--then the manpage ought to be changed. If O_NOACCESS were added, and /dev/io were not changed to match the manpage, then it could instead be changed so that read-only access grants full I/O privileges, but no access does not? > : Are there any other special devices like this in FreeBSD? > > Rewind units on tape drives? If there's no access check done, and I > open the rewind unit as joe-smoe? The close code is what does the > rewind, and you don't have enough knowledge to know if the tape was > opened r/w there. Thanks; that's a good example. Do you have an example of a specific driver so I can look at the code and see what would need to be done? _______________________________________________ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "[EMAIL PROTECTED]"
