On Wed, Dec 04, 2019 at 09:38:26PM -0500, J. Bruce Fields wrote:
> So, stuff we could do:
>
> - add an extra check of fh_export or something here.
So, I'm applying the following for now.
--b.
commit a0a906b965b0
Author: J. Bruce Fields <bfields@xxxxxxxxxx>
Date: Fri Dec 6 16:07:32 2019 -0500
nfsd4: avoid NULL deference on strange COPY compounds
With cross-server COPY we've introduced the possibility that the current
or saved filehandle might not have fh_dentry/fh_export filled in, but we
missed a place that assumed it was. I think this could be triggered by
a compound like:
PUTFH(foreign filehandle)
GETATTR
SAVEFH
COPY
First, check_if_stalefh_allowed sets no_verify on the first (PUTFH) op.
Then op_func = nfsd4_putfh runs and leaves current_fh->fh_export NULL.
need_wrongsec_check returns true, since this PUTFH has OP_IS_PUTFH_LIKE
set and GETATTR does not have OP_HANDLES_WRONGSEC set.
We should probably also consider tightening the checks in
check_if_stalefh_allowed and double-checking that we don't assume the
filehandle is verified elsewhere in the compound. But I think this
fixes the immediate issue.
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Fixes: 4e48f1cccab3 "NFSD: allow inter server COPY to have... "
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index d33c39c18cdd..5c7f622fed29 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -2368,7 +2368,8 @@ nfsd4_proc_compound(struct svc_rqst *rqstp)
if (op->opdesc->op_flags & OP_CLEAR_STATEID)
clear_current_stateid(cstate);
- if (need_wrongsec_check(rqstp))
+ if (current->fh->fh_export &&
+ need_wrongsec_check(rqstp))
op->status = check_nfsd_access(current_fh->fh_export, rqstp);
}
encode_op:
