NFSv4.x: Fix wraparound issues when validing the callback sequence id

We need to make sure that we don't allow args->csa_sequenceid == 0.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

1 files changed, 17 insertions, 26 deletions

diff --git a/fs/nfs/callback_proc.c b/fs/nfs/callback_proc.c
index 345df6309017..79c93b3bbfec 100644
--- a/fs/nfs/callback_proc.c
+++ b/fs/nfs/callback_proc.c
@@ -354,23 +354,15 @@ out:
  * a single outstanding callback request at a time.
  */
 static __be32
-validate_seqid(struct nfs4_slot_table *tbl, struct cb_sequenceargs * args)
+validate_seqid(const struct nfs4_slot_table *tbl, const struct nfs4_slot *slot,
+                const struct cb_sequenceargs * args)
 {
-        struct nfs4_slot *slot;
-
-        dprintk("%s enter. slotid %u seqid %u\n",
-                __func__, args->csa_slotid, args->csa_sequenceid);
+        dprintk("%s enter. slotid %u seqid %u, slot table seqid: %u\n",
+                __func__, args->csa_slotid, args->csa_sequenceid, slot->seq_nr);
 
         if (args->csa_slotid > tbl->server_highest_slotid)
                 return htonl(NFS4ERR_BADSLOT);
 
-        slot = tbl->slots + args->csa_slotid;
-        dprintk("%s slot table seqid: %u\n", __func__, slot->seq_nr);
-
-        /* Normal */
-        if (likely(args->csa_sequenceid == slot->seq_nr + 1))
-                goto out_ok;
-
         /* Replay */
         if (args->csa_sequenceid == slot->seq_nr) {
                 dprintk("%s seqid %u is a replay\n",
@@ -386,16 +378,14 @@ validate_seqid(struct nfs4_slot_table *tbl, struct cb_sequenceargs * args)
         }
 
         /* Wraparound */
-        if (args->csa_sequenceid == 1 && (slot->seq_nr + 1) == 0) {
-                slot->seq_nr = 1;
-                goto out_ok;
-        }
+        if (unlikely(slot->seq_nr == 0xFFFFFFFFU)) {
+                if (args->csa_sequenceid == 1)
+                        return htonl(NFS4_OK);
+        } else if (likely(args->csa_sequenceid == slot->seq_nr + 1))
+                return htonl(NFS4_OK);
 
         /* Misordered request */
         return htonl(NFS4ERR_SEQ_MISORDERED);
-out_ok:
-        tbl->highest_used_slotid = args->csa_slotid;
-        return htonl(NFS4_OK);
 }
 
 /*
@@ -486,6 +476,13 @@ __be32 nfs4_callback_sequence(struct cb_sequenceargs *args,
                 goto out_unlock;
         }
 
+        status = validate_seqid(tbl, slot, args);
+        if (status)
+                goto out_unlock;
+
+        cps->slotid = args->csa_slotid;
+        tbl->highest_used_slotid = args->csa_slotid;
+
         memcpy(&res->csr_sessionid, &args->csa_sessionid,
                sizeof(res->csr_sessionid));
         res->csr_sequenceid = args->csa_sequenceid;
@@ -493,12 +490,6 @@ __be32 nfs4_callback_sequence(struct cb_sequenceargs *args,
         res->csr_highestslotid = tbl->server_highest_slotid;
         res->csr_target_highestslotid = tbl->target_highest_slotid;
 
-        status = validate_seqid(tbl, args);
-        if (status)
-                goto out_unlock;
-
-        cps->slotid = args->csa_slotid;
-
         /* The ca_maxresponsesize_cached is 0 with no DRC */
         if (args->csa_cachethis != 0)
                 return htonl(NFS4ERR_REP_TOO_BIG_TO_CACHE);
@@ -518,7 +509,7 @@ __be32 nfs4_callback_sequence(struct cb_sequenceargs *args,
          * If CB_SEQUENCE returns an error, then the state of the slot
          * (sequence ID, cached reply) MUST NOT change.
          */
-        slot->seq_nr++;
+        slot->seq_nr = args->csa_sequenceid;
 out_unlock:
         spin_unlock(&tbl->slot_tbl_lock);