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authorJ. Bruce Fields <bfields@redhat.com>2017-05-23 19:24:40 +0300
committerJ. Bruce Fields <bfields@redhat.com>2017-05-23 21:20:58 +0300
commit9a307403d374b993061f5992a6e260c944920d0b (patch)
treecb5eb50a1bd1dd9fdb036d19a9d19963f92ddc48 /fs/nfsd/nfs4proc.c
parent9512a16b0e1217bbef73d276a67c28b5fbb46512 (diff)
downloadlinux-9a307403d374b993061f5992a6e260c944920d0b.tar.xz
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 <smayhew@redhat.com> Cc: stable@kernel.vger.org Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Diffstat (limited to 'fs/nfsd/nfs4proc.c')
-rw-r--r--fs/nfsd/nfs4proc.c13
1 files 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);