nvme: code command_id with a genctr for use-after-free validation

We cannot detect a (perhaps buggy) controller that is sending us
a completion for a request that was already completed (for example
sending a completion twice), this phenomenon was seen in the wild
a few times.

So to protect against this, we use the upper 4 msbits of the nvme sqe
command_id to use as a 4-bit generation counter and verify it matches
the existing request generation that is incrementing on every execution.

The 16-bit command_id structure now is constructed by:
| xxxx | xxxxxxxxxxxx |
  gen    request tag

This means that we are giving up some possible queue depth as 12 bits
allow for a maximum queue depth of 4095 instead of 65536, however we
never create such long queues anyways so no real harm done.

Suggested-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Acked-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Daniel Wagner <dwagner@suse.de>
Tested-by: Daniel Wagner <dwagner@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index ce33014..b9a46c5 100644 (file)
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1026,7 +1026,8 @@ blk_status_t nvme_setup_cmd(struct nvme_ns *ns, struct request *req)
                return BLK_STS_IOERR;
        }
 
-       cmd->common.command_id = req->tag;
+       nvme_req(req)->genctr++;
+       cmd->common.command_id = nvme_cid(req);
        trace_nvme_setup_cmd(req, cmd);
        return ret;
 }

diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index ab803f9..57d2ac0 100644 (file)
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -152,6 +152,7 @@ enum nvme_quirks {
 struct nvme_request {
        struct nvme_command     *cmd;
        union nvme_result       result;
+       u8                      genctr;
        u8                      retries;
        u8                      flags;
        u16                     status;
@@ -491,6 +492,49 @@ struct nvme_ctrl_ops {
        int (*get_address)(struct nvme_ctrl *ctrl, char *buf, int size);
 };
 
+/*
+ * nvme command_id is constructed as such:
+ * | xxxx | xxxxxxxxxxxx |
+ *   gen    request tag
+ */
+#define nvme_genctr_mask(gen)                  (gen & 0xf)
+#define nvme_cid_install_genctr(gen)           (nvme_genctr_mask(gen) << 12)
+#define nvme_genctr_from_cid(cid)              ((cid & 0xf000) >> 12)
+#define nvme_tag_from_cid(cid)                 (cid & 0xfff)
+
+static inline u16 nvme_cid(struct request *rq)
+{
+       return nvme_cid_install_genctr(nvme_req(rq)->genctr) | rq->tag;
+}
+
+static inline struct request *nvme_find_rq(struct blk_mq_tags *tags,
+               u16 command_id)
+{
+       u8 genctr = nvme_genctr_from_cid(command_id);
+       u16 tag = nvme_tag_from_cid(command_id);
+       struct request *rq;
+
+       rq = blk_mq_tag_to_rq(tags, tag);
+       if (unlikely(!rq)) {
+               pr_err("could not locate request for tag %#x\n",
+                       tag);
+               return NULL;
+       }
+       if (unlikely(nvme_genctr_mask(nvme_req(rq)->genctr) != genctr)) {
+               dev_err(nvme_req(rq)->ctrl->device,
+                       "request %#x genctr mismatch (got %#x expected %#x)\n",
+                       tag, genctr, nvme_genctr_mask(nvme_req(rq)->genctr));
+               return NULL;
+       }
+       return rq;
+}
+
+static inline struct request *nvme_cid_to_rq(struct blk_mq_tags *tags,
+                u16 command_id)
+{
+       return blk_mq_tag_to_rq(tags, nvme_tag_from_cid(command_id));
+}
+
 #ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
 void nvme_fault_inject_init(struct nvme_fault_inject *fault_inj,
                            const char *dev_name);
@@ -588,7 +632,8 @@ static inline void nvme_put_ctrl(struct nvme_ctrl *ctrl)
 
 static inline bool nvme_is_aen_req(u16 qid, __u16 command_id)
 {
-       return !qid && command_id >= NVME_AQ_BLK_MQ_DEPTH;
+       return !qid &&
+               nvme_tag_from_cid(command_id) >= NVME_AQ_BLK_MQ_DEPTH;
 }
 
 void nvme_complete_rq(struct request *req);

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 4880bad..0471c2c 100644 (file)
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -1010,7 +1010,7 @@ static inline void nvme_handle_cqe(struct nvme_queue *nvmeq, u16 idx)
                return;
        }
 
-       req = blk_mq_tag_to_rq(nvme_queue_tagset(nvmeq), command_id);
+       req = nvme_find_rq(nvme_queue_tagset(nvmeq), command_id);
        if (unlikely(!req)) {
                dev_warn(nvmeq->dev->ctrl.device,
                        "invalid id %d completed on queue %d\n",

diff --git a/drivers/nvme/host/rdma.c b/drivers/nvme/host/rdma.c
index 7f6b3a9..69ae676 100644 (file)
--- a/drivers/nvme/host/rdma.c
+++ b/drivers/nvme/host/rdma.c
@@ -1730,10 +1730,10 @@ static void nvme_rdma_process_nvme_rsp(struct nvme_rdma_queue *queue,
        struct request *rq;
        struct nvme_rdma_request *req;
 
-       rq = blk_mq_tag_to_rq(nvme_rdma_tagset(queue), cqe->command_id);
+       rq = nvme_find_rq(nvme_rdma_tagset(queue), cqe->command_id);
        if (!rq) {
                dev_err(queue->ctrl->ctrl.device,
-                       "tag 0x%x on QP %#x not found\n",
+                       "got bad command_id %#x on QP %#x\n",
                        cqe->command_id, queue->qp->qp_num);
                nvme_rdma_error_recovery(queue->ctrl);
                return;

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index d649b44..0a97ba0 100644 (file)
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -487,11 +487,11 @@ static int nvme_tcp_process_nvme_cqe(struct nvme_tcp_queue *queue,
 {
        struct request *rq;
 
-       rq = blk_mq_tag_to_rq(nvme_tcp_tagset(queue), cqe->command_id);
+       rq = nvme_find_rq(nvme_tcp_tagset(queue), cqe->command_id);
        if (!rq) {
                dev_err(queue->ctrl->ctrl.device,
-                       "queue %d tag 0x%x not found\n",
-                       nvme_tcp_queue_id(queue), cqe->command_id);
+                       "got bad cqe.command_id %#x on queue %d\n",
+                       cqe->command_id, nvme_tcp_queue_id(queue));
                nvme_tcp_error_recovery(&queue->ctrl->ctrl);
                return -EINVAL;
        }
@@ -508,11 +508,11 @@ static int nvme_tcp_handle_c2h_data(struct nvme_tcp_queue *queue,
 {
        struct request *rq;
 
-       rq = blk_mq_tag_to_rq(nvme_tcp_tagset(queue), pdu->command_id);
+       rq = nvme_find_rq(nvme_tcp_tagset(queue), pdu->command_id);
        if (!rq) {
                dev_err(queue->ctrl->ctrl.device,
-                       "queue %d tag %#x not found\n",
-                       nvme_tcp_queue_id(queue), pdu->command_id);
+                       "got bad c2hdata.command_id %#x on queue %d\n",
+                       pdu->command_id, nvme_tcp_queue_id(queue));
                return -ENOENT;
        }
 
@@ -606,7 +606,7 @@ static int nvme_tcp_setup_h2c_data_pdu(struct nvme_tcp_request *req,
        data->hdr.plen =
                cpu_to_le32(data->hdr.hlen + hdgst + req->pdu_len + ddgst);
        data->ttag = pdu->ttag;
-       data->command_id = rq->tag;
+       data->command_id = nvme_cid(rq);
        data->data_offset = cpu_to_le32(req->data_sent);
        data->data_length = cpu_to_le32(req->pdu_len);
        return 0;
@@ -619,11 +619,11 @@ static int nvme_tcp_handle_r2t(struct nvme_tcp_queue *queue,
        struct request *rq;
        int ret;
 
-       rq = blk_mq_tag_to_rq(nvme_tcp_tagset(queue), pdu->command_id);
+       rq = nvme_find_rq(nvme_tcp_tagset(queue), pdu->command_id);
        if (!rq) {
                dev_err(queue->ctrl->ctrl.device,
-                       "queue %d tag %#x not found\n",
-                       nvme_tcp_queue_id(queue), pdu->command_id);
+                       "got bad r2t.command_id %#x on queue %d\n",
+                       pdu->command_id, nvme_tcp_queue_id(queue));
                return -ENOENT;
        }
        req = blk_mq_rq_to_pdu(rq);
@@ -703,7 +703,7 @@ static int nvme_tcp_recv_data(struct nvme_tcp_queue *queue, struct sk_buff *skb,
 {
        struct nvme_tcp_data_pdu *pdu = (void *)queue->pdu;
        struct request *rq =
-               blk_mq_tag_to_rq(nvme_tcp_tagset(queue), pdu->command_id);
+               nvme_cid_to_rq(nvme_tcp_tagset(queue), pdu->command_id);
        struct nvme_tcp_request *req = blk_mq_rq_to_pdu(rq);
 
        while (true) {
@@ -796,8 +796,8 @@ static int nvme_tcp_recv_ddgst(struct nvme_tcp_queue *queue,
        }
 
        if (pdu->hdr.flags & NVME_TCP_F_DATA_SUCCESS) {
-               struct request *rq = blk_mq_tag_to_rq(nvme_tcp_tagset(queue),
-                                               pdu->command_id);
+               struct request *rq = nvme_cid_to_rq(nvme_tcp_tagset(queue),
+                                       pdu->command_id);
 
                nvme_tcp_end_request(rq, NVME_SC_SUCCESS);
                queue->nr_cqe++;

diff --git a/drivers/nvme/target/loop.c b/drivers/nvme/target/loop.c
index 3a17a7e..0285ccc 100644 (file)
--- a/drivers/nvme/target/loop.c
+++ b/drivers/nvme/target/loop.c
@@ -107,10 +107,10 @@ static void nvme_loop_queue_response(struct nvmet_req *req)
        } else {
                struct request *rq;
 
-               rq = blk_mq_tag_to_rq(nvme_loop_tagset(queue), cqe->command_id);
+               rq = nvme_find_rq(nvme_loop_tagset(queue), cqe->command_id);
                if (!rq) {
                        dev_err(queue->ctrl->ctrl.device,
-                               "tag 0x%x on queue %d not found\n",
+                               "got bad command_id %#x on queue %d\n",
                                cqe->command_id, nvme_loop_queue_idx(queue));
                        return;
                }