From 9a307403d374b993061f5992a6e260c944920d0b Mon Sep 17 00:00:00 2001 From: "J. Bruce Fields" Date: Tue, 23 May 2017 12:24:40 -0400 Subject: [PATCH] nfsd4: fix null dereference on replay 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 Cc: stable@kernel.vger.org Signed-off-by: J. Bruce Fields --- fs/nfsd/nfs4proc.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c index c453a1998e00..dadb3bf305b2 100644 --- a/fs/nfsd/nfs4proc.c +++ b/fs/nfsd/nfs4proc.c @@ -1769,6 +1769,12 @@ nfsd4_proc_compound(struct svc_rqst *rqstp, 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); @@ -1779,14 +1785,7 @@ nfsd4_proc_compound(struct svc_rqst *rqstp, 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); -- 2.20.1