Re: question about fh_copy

[Ming Zhang <blackmagic02881@gmail.com>]

On Sun, 2007-01-28 at 18:01 -0500, J. Bruce Fields wrote:
> On Sat, Jan 27, 2007 at 10:20:08AM -0500, Ming Zhang wrote:
> > A question about fh_copy(). This function is called many times on
> > argument passed directly from nfs clients. If a malicious nfs client
> > forge a fh, then fh_copy can invoke oops quite easily.
> 
> I don't see how; can you explain?

svc_process at http://lxr.linux.no/source/net/sunrpc/svc.c?v=2.6.18#L386
invoke a rpc processing function, for example, nfsd3_proc_getattr
then at http://lxr.linux.no/source/fs/nfsd/nfs3proc.c?v=2.6.18#L64
invoke fh_copy before fh_verify. since src coming from client, client
can forge a fh to let code
http://lxr.linux.no/source/include/linux/nfsd/nfsfh.h?v=2.6.18#L222 get
executed. if fh_dentry is a invalid pointer, it can get oops.

or think in another way, if the fh will always be valid with all
contents, then what is the point to call fh_verify to do "sanity checks
on the dentry in a client file handle", quoted from fh_verify comment at
http://lxr.linux.no/source/fs/nfsd/nfsfh.c?v=2.6.18#L105?

Ming

> 
> --b.
-- 
http://blackmagic02881.wordpress.com/


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