Re: [RFC] ext2 and ext3 block reservations can be bypassed

[Peter Chubb]

>>>>> "elladan" == elladan  <[e-mail]> writes:

elladan> It's perfectly legal for the shell to sit around with a file
elladan> open and pass it off to a child, even if the disk is full.

elladan> It's also perfectly legal for root to write to the fd, even
elladan> if the disk is full (for normal users).

elladan> It just happens that the suid program wasn't the one who
elladan> chose what file it was going to write stdout to - the shell
elladan> did.

This is why in SVr4, struct cred is cloned at open time, and passed
down to each VFS operation.

There's a choice of security modules here--- should the credentials
of the opener or the credentials of the writer determine the use of
the extra space?  I think in this case it ought to be the credentials
of the opener.  Also, I'm not sure that mount(8) should be a setuid
program. (I know it's convenient for floppy mounts, but I'd rather
they were handled by autofs)

Peter C