Re: Bug/security hole in NFS cache (1.3.68)

Matthias Urlichs (smurf@smurf.noris.de)
Sat, 24 Feb 1996 23:25:09 +0100


In linux.dev.kernel, article <199602231112.AA08267@beatrix.fss.fokker.n=
l>,
"Robert H. de Vries" <rhdv@fss.fokker.nl> writes:
> It seems that the NFS cache keeps its data without regard of who
> requested it the first time.

Files don't change their contents depending on who requests them.

> If you read a file as root without read permission, you get a file wi=
th NUL
> characters only.

This is the real bug. If a file can't be read, the error (from NFS, in =
this
case) should be propagated to whoever is requesting the file, and the
buffer should stay invalid.

The other problem (root reading the file which previously has been read
by the user is able to read the file) is not so easy to solve. From the
point of view of the client, the reply is 100% correct -- root is able =
to
read any file, right? NFS, unfortunately, doesn't tell the client that =
root
isn't root. :-(

--=20
CTY (city) n. The terminal physically associated with a computer's
operating console.
-- From the AI Hackers' Dictionary
--=20
Matthias Urlichs \ XLink-POP N=FCrnberg | EMail: urlichs@smurf.=
noris.de
Schleiermacherstra=DFe 12 \ Unix+Linux+Mac | Phone: ...please use =
email.
90491 N=FCrnberg (Germany) \ Consulting+Networking+Programming+etc'i=
ng 42
PGP: 1B 89 E2 1C 43 EA 80 44 15 D2 29 CF C6 C7 E0 DE=20
Click <A HREF=3D"http://smurf.noris.de/~smurf/finger">here</A>.