[PATCH] nvmet: copy the hostid into the ctrl before creating PR pc_refs

[PATCH] nvmet: copy the hostid into the ctrl before creating PR pc_refs

[Guixin Liu]

Commit 6202783184bf ("nvmet: Improve nvmet_alloc_ctrl() interface and
implementation") added a second uuid_copy() of args->hostid near the end
of nvmet_alloc_ctrl(), and commit 7b658153f1b8 ("nvmet: Remove duplicate
uuid_copy") removed the original copy that sat before
nvmet_ctrl_init_pr() instead of the new one.

Since then nvmet_ctrl_init_pr() snapshots ctrl->hostid into the
per-controller per-namespace reservation refs while the uuid_copy()
from the connect data runs later, after the controller is published.
The ctrl is allocated with kzalloc(), so every pc_ref created on this
path stores the nil UUID.

pc_ref->hostid has a single consumer: nvmet_pr_set_ctrl_to_abort()
matches it against the preempted registrant's hostid to kill and drain
the victim's in-flight I/O for Preempt and Abort.  The match can never
hit with the nil UUID, so whenever a namespace with reservations
enabled exists before a host connects, which includes every reconnect,
Preempt and Abort silently degrades into a plain Preempt: the
preempting host sees success while the victim's in-flight I/O is still
in the air.

Copy the hostid where the rest of the connect data is consumed, before
the controller is published and before nvmet_ctrl_init_pr() takes its
snapshot.

Fixes: 7b658153f1b8 ("nvmet: Remove duplicate uuid_copy")
Cc: stable@vger.kernel.org
Signed-off-by: Guixin Liu <kanie@linux.alibaba.com>
---
 drivers/nvme/target/core.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
index 43871a8f56ca..8c8c8627871f 100644
--- a/drivers/nvme/target/core.c
+++ b/drivers/nvme/target/core.c
@@ -1648,6 +1648,8 @@ struct nvmet_ctrl *nvmet_alloc_ctrl(struct nvmet_alloc_ctrl_args *args)
 	INIT_DELAYED_WORK(&ctrl->ka_work, nvmet_keep_alive_timer);
 
 	memcpy(ctrl->hostnqn, args->hostnqn, NVMF_NQN_SIZE);
+	if (args->hostid)
+		uuid_copy(&ctrl->hostid, args->hostid);
 
 	kref_init(&ctrl->ref);
 	ctrl->subsys = subsys;
@@ -1706,9 +1708,6 @@ struct nvmet_ctrl *nvmet_alloc_ctrl(struct nvmet_alloc_ctrl_args *args)
 
 	nvmet_start_keep_alive_timer(ctrl);
 
-	if (args->hostid)
-		uuid_copy(&ctrl->hostid, args->hostid);
-
 	dhchap_status = nvmet_setup_auth(ctrl, args->sq, false);
 	if (dhchap_status) {
 		pr_err("Failed to setup authentication, dhchap status %u\n",
-- 
2.43.7

Re: [PATCH] nvmet: copy the hostid into the ctrl before creating PR pc_refs

[Daniel Wagner]

On Wed, Sep 16, 2026 at 07:42:54PM +0800, Guixin Liu wrote:
> Commit 6202783184bf ("nvmet: Improve nvmet_alloc_ctrl() interface and
> implementation") added a second uuid_copy() of args->hostid near the end
> of nvmet_alloc_ctrl(), and commit 7b658153f1b8 ("nvmet: Remove duplicate
> uuid_copy") removed the original copy that sat before
> nvmet_ctrl_init_pr() instead of the new one.
> 
> Since then nvmet_ctrl_init_pr() snapshots ctrl->hostid into the
> per-controller per-namespace reservation refs while the uuid_copy()
> from the connect data runs later, after the controller is published.
> The ctrl is allocated with kzalloc(), so every pc_ref created on this
> path stores the nil UUID.
> 
> pc_ref->hostid has a single consumer: nvmet_pr_set_ctrl_to_abort()
> matches it against the preempted registrant's hostid to kill and drain
> the victim's in-flight I/O for Preempt and Abort.  The match can never
> hit with the nil UUID, so whenever a namespace with reservations
> enabled exists before a host connects, which includes every reconnect,
> Preempt and Abort silently degrades into a plain Preempt: the
> preempting host sees success while the victim's in-flight I/O is still
> in the air.
> 
> Copy the hostid where the rest of the connect data is consumed, before
> the controller is published and before nvmet_ctrl_init_pr() takes its
> snapshot.
> 
> Fixes: 7b658153f1b8 ("nvmet: Remove duplicate uuid_copy")
> Cc: stable@vger.kernel.org
> Signed-off-by: Guixin Liu <kanie@linux.alibaba.com>

Besides fixing this bug, it makes more sense to pair the hostid memcpy
with the hostnqn one.

Reviewed-by: Daniel Wagner <dwagner@suse.de>

Re: [PATCH] nvmet: copy the hostid into the ctrl before creating PR pc_refs

[Nilay Shroff]

On 9/16/26 5:12 PM, Guixin Liu wrote:
> Commit 6202783184bf ("nvmet: Improve nvmet_alloc_ctrl() interface and
> implementation") added a second uuid_copy() of args->hostid near the end
> of nvmet_alloc_ctrl(), and commit 7b658153f1b8 ("nvmet: Remove duplicate
> uuid_copy") removed the original copy that sat before
> nvmet_ctrl_init_pr() instead of the new one.
> 
> Since then nvmet_ctrl_init_pr() snapshots ctrl->hostid into the
> per-controller per-namespace reservation refs while the uuid_copy()
> from the connect data runs later, after the controller is published.
> The ctrl is allocated with kzalloc(), so every pc_ref created on this
> path stores the nil UUID.
> 
> pc_ref->hostid has a single consumer: nvmet_pr_set_ctrl_to_abort()
> matches it against the preempted registrant's hostid to kill and drain
> the victim's in-flight I/O for Preempt and Abort.  The match can never
> hit with the nil UUID, so whenever a namespace with reservations
> enabled exists before a host connects, which includes every reconnect,
> Preempt and Abort silently degrades into a plain Preempt: the
> preempting host sees success while the victim's in-flight I/O is still
> in the air.
> 
> Copy the hostid where the rest of the connect data is consumed, before
> the controller is published and before nvmet_ctrl_init_pr() takes its
> snapshot.
> 
> Fixes: 7b658153f1b8 ("nvmet: Remove duplicate uuid_copy")
> Cc:stable@vger.kernel.org
> Signed-off-by: Guixin Liu<kanie@linux.alibaba.com>

Looks good to me.
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>

Re: [PATCH] nvmet: copy the hostid into the ctrl before creating PR pc_refs

[Christoph Hellwig]

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH] nvmet: copy the hostid into the ctrl before creating PR pc_refs

[Hannes Reinecke]

On 9/16/26 1:42 PM, Guixin Liu wrote:
> Commit 6202783184bf ("nvmet: Improve nvmet_alloc_ctrl() interface and
> implementation") added a second uuid_copy() of args->hostid near the end
> of nvmet_alloc_ctrl(), and commit 7b658153f1b8 ("nvmet: Remove duplicate
> uuid_copy") removed the original copy that sat before
> nvmet_ctrl_init_pr() instead of the new one.
> 
> Since then nvmet_ctrl_init_pr() snapshots ctrl->hostid into the
> per-controller per-namespace reservation refs while the uuid_copy()
> from the connect data runs later, after the controller is published.
> The ctrl is allocated with kzalloc(), so every pc_ref created on this
> path stores the nil UUID.
> 
> pc_ref->hostid has a single consumer: nvmet_pr_set_ctrl_to_abort()
> matches it against the preempted registrant's hostid to kill and drain
> the victim's in-flight I/O for Preempt and Abort.  The match can never
> hit with the nil UUID, so whenever a namespace with reservations
> enabled exists before a host connects, which includes every reconnect,
> Preempt and Abort silently degrades into a plain Preempt: the
> preempting host sees success while the victim's in-flight I/O is still
> in the air.
> 
> Copy the hostid where the rest of the connect data is consumed, before
> the controller is published and before nvmet_ctrl_init_pr() takes its
> snapshot.
> 
> Fixes: 7b658153f1b8 ("nvmet: Remove duplicate uuid_copy")
> Cc: stable@vger.kernel.org
> Signed-off-by: Guixin Liu <kanie@linux.alibaba.com>
> ---
>   drivers/nvme/target/core.c | 5 ++---
>   1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
> index 43871a8f56ca..8c8c8627871f 100644
> --- a/drivers/nvme/target/core.c
> +++ b/drivers/nvme/target/core.c
> @@ -1648,6 +1648,8 @@ struct nvmet_ctrl *nvmet_alloc_ctrl(struct nvmet_alloc_ctrl_args *args)
>   	INIT_DELAYED_WORK(&ctrl->ka_work, nvmet_keep_alive_timer);
>   
>   	memcpy(ctrl->hostnqn, args->hostnqn, NVMF_NQN_SIZE);
> +	if (args->hostid)
> +		uuid_copy(&ctrl->hostid, args->hostid);
>   
>   	kref_init(&ctrl->ref);
>   	ctrl->subsys = subsys;
> @@ -1706,9 +1708,6 @@ struct nvmet_ctrl *nvmet_alloc_ctrl(struct nvmet_alloc_ctrl_args *args)
>   
>   	nvmet_start_keep_alive_timer(ctrl);
>   
> -	if (args->hostid)
> -		uuid_copy(&ctrl->hostid, args->hostid);
> -
>   	dhchap_status = nvmet_setup_auth(ctrl, args->sq, false);
>   	if (dhchap_status) {
>   		pr_err("Failed to setup authentication, dhchap status %u\n",
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich

Re: [PATCH] nvmet: copy the hostid into the ctrl before creating PR pc_refs

[Keith Busch]

On Wed, Sep 16, 2026 at 07:42:54PM +0800, Guixin Liu wrote:
> Commit 6202783184bf ("nvmet: Improve nvmet_alloc_ctrl() interface and
> implementation") added a second uuid_copy() of args->hostid near the end
> of nvmet_alloc_ctrl(), and commit 7b658153f1b8 ("nvmet: Remove duplicate
> uuid_copy") removed the original copy that sat before
> nvmet_ctrl_init_pr() instead of the new one.

Thanks, applied to nvme-7.3.