Re: [PATCH v2] nvme-tcp: fix NULL queue->ctrl dereference on reconnect
From: Hannes Reinecke
Date: Wed Oct 28 2026 - 03:39:47 EST
On 10/28/26 3:43 AM, Christian Aurich Zanettini Martins wrote:
Since commit 61b0ed3be81b ("nvme-tcp: parallelize I/O queue allocation
and startup"), a reconnect that gets more I/O queues than before grows
the tag set before the new queues are allocated. queue->ctrl is only
set by nvme_tcp_alloc_queue(), so I/O submitted in between reaches
nvme_tcp_queue_rq() on a queue that was never allocated and
dereferences a NULL queue->ctrl:
BUG: kernel NULL pointer dereference, address: 00000000000002ac
RIP: 0010:nvme_tcp_queue_rq+0x33/0x3b0
Add nvme_tcp_init_queue() for the queue fields that do not depend on
the connection and call it for every queue when allocating the
controller. Such requests are then requeued like on any other queue
that is not live. send_mutex and io_work move there as well, and the
helper's mutexes are all destroyed when the controller is freed, like
queue_lock already is.
Fixes: 61b0ed3be81b ("nvme-tcp: parallelize I/O queue allocation and startup")
Suggested-by: Keith Busch <kbusch@xxxxxxxxxx>
Signed-off-by: Christian Aurich Zanettini Martins <christian.aurichzm@xxxxxxxxx>
---
v2:
- Rebase on Guixin's v4 "nvme-tcp: Validate the queue state under the
queue lock in the address attribute" and move its queue_lock init
into the helper
- Also move send_mutex and io_work into the helper, and destroy
send_mutex and pf_cache_lock next to queue_lock in
nvme_tcp_free_ctrl() (Keith)
- Left in nvme_tcp_alloc_queue(): req_list and send_list, as resetting
them drops entries left over from the previous connection, and the
lockdep keys, which are per socket instance since commit 19bdb70c77d3
("nvme-tcp: lockdep: use dynamic lockdep keys per socket instance")
Based on nvme-7.4 (9afc1b71d963) with "nvme-tcp: fix request PDU size
when header digest is enabled" and Guixin's v4 on top. The last hunk
assumes the conflict between those two in nvme_tcp_alloc_ctrl() is
resolved by keeping both loop bodies and both comments. I can resend on
top of nvme-7.4 once both are there.
Reproduced in QEMU with nvmet-tcp over loopback and
CONFIG_NVME_MULTIPATH=n: connect with attr_qid_max=2, keep direct reads
running on the CPUs that map to the new hw queues, then raise
attr_qid_max to 4. Before the patch the host oopsed as above within two
tries in each of three boots; with v2, 8 of 8 tries went live, with and
without lockdep. 30 resets under digest I/O, with a reader looping on
the address attribute, also pass and are clean with lockdep.
drivers/nvme/host/tcp.c | 58 ++++++++++++++++++++---------------------
1 file changed, 29 insertions(+), 29 deletions(-)
diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 4ada1ff120e2..77bc530ae0a6 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -1559,7 +1559,6 @@ static void nvme_tcp_free_queue(struct nvme_ctrl *nctrl, int qid)
memalloc_noio_restore(noio_flag);
kfree(queue->pdu);
- mutex_destroy(&queue->send_mutex);
#ifdef CONFIG_DEBUG_LOCK_ALLOC
lockdep_unregister_key(&queue->nvme_tcp_sk_key);
@@ -1987,6 +1986,26 @@ static int nvme_tcp_start_tls(struct nvme_ctrl *nctrl,
return ret;
}
+/*
+ * The I/O tag set is allocated, and grown on reconnect, before the queues are
+ * connected, so blk-mq can initialize requests on a queue, and dispatch to it,
+ * before nvme_tcp_alloc_queue() has run for it. Set up the fields that do not
+ * depend on the connection once, when allocating the controller, and keep them
+ * until the controller is freed.
+ */
+static void nvme_tcp_init_queue(struct nvme_tcp_ctrl *ctrl, int qid)
+{
+ struct nvme_tcp_queue *queue = &ctrl->queues[qid];
+
+ queue->ctrl = ctrl;
+ mutex_init(&queue->queue_lock);
+ mutex_init(&queue->send_mutex);
+ mutex_init(&queue->pf_cache_lock);
+ INIT_WORK(&queue->io_work, nvme_tcp_io_work);
+ queue->hdr_digest = ctrl->ctrl.opts->hdr_digest;
+ queue->data_digest = ctrl->ctrl.opts->data_digest;
+}
+
static int nvme_tcp_alloc_queue(struct nvme_ctrl *nctrl, int qid,
key_serial_t pskid)
{
@@ -1995,11 +2014,8 @@ static int nvme_tcp_alloc_queue(struct nvme_ctrl *nctrl, int qid,
int ret, rcv_pdu_size;
struct file *sock_file;
- queue->ctrl = ctrl;
init_llist_head(&queue->req_list);
INIT_LIST_HEAD(&queue->send_list);
- mutex_init(&queue->send_mutex);
- INIT_WORK(&queue->io_work, nvme_tcp_io_work);
if (qid > 0)
queue->cmnd_capsule_len = nctrl->ioccsz * 16;
@@ -2013,14 +2029,12 @@ static int nvme_tcp_alloc_queue(struct nvme_ctrl *nctrl, int qid,
if (ret) {
dev_err(nctrl->device,
"failed to create socket: %d\n", ret);
- goto err_destroy_mutex;
+ return ret;
}
sock_file = sock_alloc_file(queue->sock, O_CLOEXEC, NULL);
- if (IS_ERR(sock_file)) {
- ret = PTR_ERR(sock_file);
- goto err_destroy_mutex;
- }
+ if (IS_ERR(sock_file))
+ return PTR_ERR(sock_file);
sk_net_refcnt_upgrade(queue->sock->sk);
@@ -2088,8 +2102,6 @@ static int nvme_tcp_alloc_queue(struct nvme_ctrl *nctrl, int qid,
}
}
- queue->data_digest = nctrl->opts->data_digest;
-
rcv_pdu_size = sizeof(struct nvme_tcp_rsp_pdu) +
nvme_tcp_hdgst_len(queue);
queue->pdu = kmalloc(rcv_pdu_size, GFP_KERNEL);
@@ -2136,8 +2148,6 @@ static int nvme_tcp_alloc_queue(struct nvme_ctrl *nctrl, int qid,
lockdep_unregister_key(&queue->nvme_tcp_sk_key);
lockdep_unregister_key(&queue->nvme_tcp_slock_key);
#endif
-err_destroy_mutex:
- mutex_destroy(&queue->send_mutex);
return ret;
}
@@ -2838,8 +2848,11 @@ static void nvme_tcp_free_ctrl(struct nvme_ctrl *nctrl)
nvmf_free_options(nctrl->opts);
free_ctrl:
put_net(ctrl->net);
- for (i = 0; i < nr_queues; i++)
+ for (i = 0; i < nr_queues; i++) {
mutex_destroy(&ctrl->queues[i].queue_lock);
+ mutex_destroy(&ctrl->queues[i].send_mutex);
+ mutex_destroy(&ctrl->queues[i].pf_cache_lock);
+ }
Might be an idea to use a new function 'nvme_tcp_exit_queue()'
here for symmetry with 'nvme_tcp_init_queue()'.
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@xxxxxxx +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich