nfsd4: fix null dereference on replay
commit 9a307403d374b993061f5992a6e260c944920d0b upstream.
if we receive a compound such that:
- the sessionid, slot, and sequence number in the SEQUENCE op
match a cached succesful reply with N ops, and
- the Nth operation of the compound is a PUTFH, PUTPUBFH,
PUTROOTFH, or RESTOREFH,
then nfsd4_sequence will return 0 and set cstate->status to
nfserr_replay_cache. The current filehandle will not be set. This will
cause us to call check_nfsd_access with first argument NULL.
To nfsd4_compound it looks like we just succesfully executed an
operation that set a filehandle, but the current filehandle is not set.
Fix this by moving the nfserr_replay_cache earlier. There was never any
reason to have it after the encode_op label, since the only case where
he hit that is when opdesc->op_func sets it.
Note that there are two ways we could hit this case:
- a client is resending a previously sent compound that ended
with one of the four PUTFH-like operations, or
- a client is sending a *new* compound that (incorrectly) shares
sessionid, slot, and sequence number with a previously sent
compound, and the length of the previously sent compound
happens to match the position of a PUTFH-like operation in the
new compound.
The second is obviously incorrect client behavior. The first is also
very strange--the only purpose of a PUTFH-like operation is to set the
current filehandle to be used by the following operation, so there's no
point in having it as the last in a compound.
So it's likely this requires a buggy or malicious client to reproduce.
Reported-by: Scott Mayhew <smayhew@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 650226f..022d958 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -1783,6 +1783,12 @@
opdesc->op_get_currentstateid(cstate, &op->u);
op->status = opdesc->op_func(rqstp, cstate, &op->u);
+ /* Only from SEQUENCE */
+ if (cstate->status == nfserr_replay_cache) {
+ dprintk("%s NFS4.1 replay from cache\n", __func__);
+ status = op->status;
+ goto out;
+ }
if (!op->status) {
if (opdesc->op_set_currentstateid)
opdesc->op_set_currentstateid(cstate, &op->u);
@@ -1793,14 +1799,7 @@
if (need_wrongsec_check(rqstp))
op->status = check_nfsd_access(current_fh->fh_export, rqstp);
}
-
encode_op:
- /* Only from SEQUENCE */
- if (cstate->status == nfserr_replay_cache) {
- dprintk("%s NFS4.1 replay from cache\n", __func__);
- status = op->status;
- goto out;
- }
if (op->status == nfserr_replay_me) {
op->replay = &cstate->replay_owner->so_replay;
nfsd4_encode_replay(&resp->xdr, op);