Re: [PATCH 3/3] RDMA/srpt: Fix a use-after-free

["lizhijian@fujitsu.com" <lizhijian@fujitsu.com>]

On 27/07/2022 05:21, Bart Van Assche wrote:
> Change the LIO port members inside struct srpt_port from regular members
> into pointers. Allocate the LIO port data structures from inside
> srpt_make_tport() and free these from inside srpt_make_tport(). Keep struct
> srpt_device as long as either an RDMA port or a LIO target port is
> associated with it. This patch decouples the lifetime of struct srpt_port
> (controlled by the RDMA core) and struct srpt_port_id (controlled by LIO).
> This patch fixes the following KASAN complaint:
>
> BUG: KASAN: use-after-free in srpt_enable_tpg+0x31/0x70 [ib_srpt]
> Read of size 8 at addr ffff888141cc34b8 by task check/5093
>
> Call Trace:
>   <TASK>
>   show_stack+0x4e/0x53
>   dump_stack_lvl+0x51/0x66
>   print_address_description.constprop.0.cold+0xea/0x41e
>   print_report.cold+0x90/0x205
>   kasan_report+0xb9/0xf0
>   __asan_load8+0x69/0x90
>   srpt_enable_tpg+0x31/0x70 [ib_srpt]
>   target_fabric_tpg_base_enable_store+0xe2/0x140 [target_core_mod]
>   configfs_write_iter+0x18b/0x210
>   new_sync_write+0x1f2/0x2f0
>   vfs_write+0x3e3/0x540
>   ksys_write+0xbb/0x140
>   __x64_sys_write+0x42/0x50
>   do_syscall_64+0x34/0x80
>   entry_SYSCALL_64_after_hwframe+0x46/0xb0
>   </TASK>

I tested patches with blktests/srp, it works well and the UAF is gone.


> Reported-by: Li Zhijian <lizhijian@fujitsu.com>
> Cc: Li Zhijian <lizhijian@fujitsu.com>
> Cc: Hillf Danton <hdanton@sina.com>
> Cc: Mike Christie <michael.christie@oracle.com>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> ---
>   drivers/infiniband/ulp/srpt/ib_srpt.c | 133 ++++++++++++++++++--------
>   drivers/infiniband/ulp/srpt/ib_srpt.h |  10 +-
>   2 files changed, 96 insertions(+), 47 deletions(-)
>
> diff --git a/drivers/infiniband/ulp/srpt/ib_srpt.c b/drivers/infiniband/ulp/srpt/ib_srpt.c
> index 1fbce9225424..8d9eb1210d3b 100644
> --- a/drivers/infiniband/ulp/srpt/ib_srpt.c
> +++ b/drivers/infiniband/ulp/srpt/ib_srpt.c
> @@ -565,18 +565,12 @@ static int srpt_refresh_port(struct srpt_port *sport)
>   	if (ret)
>   		return ret;
>   
> -	sport->port_guid_id.wwn.priv = sport;
>   	srpt_format_guid(sport->guid_name, ARRAY_SIZE(sport->guid_name),
>   			 &sport->gid.global.interface_id);
> -	memcpy(sport->port_guid_id.name, sport->guid_name,
> -	       ARRAY_SIZE(sport->guid_name));
> -	sport->port_gid_id.wwn.priv = sport;
>   	snprintf(sport->gid_name, ARRAY_SIZE(sport->gid_name),
>   		 "0x%016llx%016llx",
>   		 be64_to_cpu(sport->gid.global.subnet_prefix),
>   		 be64_to_cpu(sport->gid.global.interface_id));
> -	memcpy(sport->port_gid_id.name, sport->gid_name,
> -	       ARRAY_SIZE(sport->gid_name));
>   
>   	if (rdma_protocol_iwarp(sport->sdev->device, sport->port))
>   		return 0;
> @@ -2317,31 +2311,35 @@ static int srpt_cm_req_recv(struct srpt_device *const sdev,
>   	tag_num = ch->rq_size;
>   	tag_size = 1; /* ib_srpt does not use se_sess->sess_cmd_map */
>   
> -	mutex_lock(&sport->port_guid_id.mutex);
> -	list_for_each_entry(stpg, &sport->port_guid_id.tpg_list, entry) {
> -		if (!IS_ERR_OR_NULL(ch->sess))
> -			break;
> -		ch->sess = target_setup_session(&stpg->tpg, tag_num,
> +	if (sport->guid_id) {
> +		mutex_lock(&sport->guid_id->mutex);
> +		list_for_each_entry(stpg, &sport->guid_id->tpg_list, entry) {
> +			if (!IS_ERR_OR_NULL(ch->sess))
> +				break;
> +			ch->sess = target_setup_session(&stpg->tpg, tag_num,
>   						tag_size, TARGET_PROT_NORMAL,
>   						ch->sess_name, ch, NULL);
> +		}
> +		mutex_unlock(&sport->guid_id->mutex);
>   	}
> -	mutex_unlock(&sport->port_guid_id.mutex);
>   
> -	mutex_lock(&sport->port_gid_id.mutex);
> -	list_for_each_entry(stpg, &sport->port_gid_id.tpg_list, entry) {
> -		if (!IS_ERR_OR_NULL(ch->sess))
> -			break;
> -		ch->sess = target_setup_session(&stpg->tpg, tag_num,
> +	if (sport->gid_id) {
> +		mutex_lock(&sport->gid_id->mutex);
> +		list_for_each_entry(stpg, &sport->gid_id->tpg_list, entry) {
> +			if (!IS_ERR_OR_NULL(ch->sess))
> +				break;
> +			ch->sess = target_setup_session(&stpg->tpg, tag_num,
>   					tag_size, TARGET_PROT_NORMAL, i_port_id,
>   					ch, NULL);
> -		if (!IS_ERR_OR_NULL(ch->sess))
> -			break;
> -		/* Retry without leading "0x" */
> -		ch->sess = target_setup_session(&stpg->tpg, tag_num,
> +			if (!IS_ERR_OR_NULL(ch->sess))
> +				break;
> +			/* Retry without leading "0x" */
> +			ch->sess = target_setup_session(&stpg->tpg, tag_num,
>   						tag_size, TARGET_PROT_NORMAL,
>   						i_port_id + 2, ch, NULL);
> +		}
> +		mutex_unlock(&sport->gid_id->mutex);
>   	}
> -	mutex_unlock(&sport->port_gid_id.mutex);
>   
>   	if (IS_ERR_OR_NULL(ch->sess)) {
>   		WARN_ON_ONCE(ch->sess == NULL);
> @@ -2986,7 +2984,12 @@ static int srpt_release_sport(struct srpt_port *sport)
>   	return 0;
>   }
>   
> -static struct se_wwn *__srpt_lookup_wwn(const char *name)
> +struct port_and_port_id {
> +	struct srpt_port *sport;
> +	struct srpt_port_id **port_id;
> +};
> +
> +static struct port_and_port_id __srpt_lookup_port(const char *name)
>   {
>   	struct ib_device *dev;
>   	struct srpt_device *sdev;
> @@ -3001,25 +3004,38 @@ static struct se_wwn *__srpt_lookup_wwn(const char *name)
>   		for (i = 0; i < dev->phys_port_cnt; i++) {
>   			sport = &sdev->port[i];
>   
> -			if (strcmp(sport->port_guid_id.name, name) == 0)
> -				return &sport->port_guid_id.wwn;
> -			if (strcmp(sport->port_gid_id.name, name) == 0)
> -				return &sport->port_gid_id.wwn;
> +			if (strcmp(sport->guid_name, name) == 0) {
> +				kref_get(&sdev->refcnt);
> +				return (struct port_and_port_id){
> +					sport, &sport->guid_id};
> +			}
> +			if (strcmp(sport->gid_name, name) == 0) {
> +				kref_get(&sdev->refcnt);
> +				return (struct port_and_port_id){
> +					sport, &sport->gid_id};
> +			}
>   		}
>   	}
>   
> -	return NULL;
> +	return (struct port_and_port_id){};
>   }
>   
> -static struct se_wwn *srpt_lookup_wwn(const char *name)
> +/**
> + * srpt_lookup_port() - Look up an RDMA port by name
> + * @name: ASCII port name
> + *
> + * Increments the RDMA port reference count if an RDMA port pointer is returned.
> + * The caller must drop that reference count by calling srpt_port_put_ref().
> + */
> +static struct port_and_port_id srpt_lookup_port(const char *name)
>   {
> -	struct se_wwn *wwn;
> +	struct port_and_port_id papi;
>   
>   	spin_lock(&srpt_dev_lock);
> -	wwn = __srpt_lookup_wwn(name);
> +	papi = __srpt_lookup_port(name);
>   	spin_unlock(&srpt_dev_lock);
>   
> -	return wwn;
> +	return papi;
>   }
>   
>   static void srpt_free_srq(struct srpt_device *sdev)
> @@ -3198,10 +3214,6 @@ static int srpt_add_one(struct ib_device *device)
>   		sport->port_attrib.srp_sq_size = DEF_SRPT_SQ_SIZE;
>   		sport->port_attrib.use_srq = false;
>   		INIT_WORK(&sport->work, srpt_refresh_port_work);
> -		mutex_init(&sport->port_guid_id.mutex);
> -		INIT_LIST_HEAD(&sport->port_guid_id.tpg_list);
> -		mutex_init(&sport->port_gid_id.mutex);
> -		INIT_LIST_HEAD(&sport->port_gid_id.tpg_list);
>   
>   		ret = srpt_refresh_port(sport);
>   		if (ret) {
> @@ -3295,6 +3307,7 @@ static int srpt_check_false(struct se_portal_group *se_tpg)
>   
>   static struct srpt_port *srpt_tpg_to_sport(struct se_portal_group *tpg)
>   {
> +	BUG_ON(!tpg->se_tpg_wwn->priv);
>   	return tpg->se_tpg_wwn->priv;
>   }
>   
> @@ -3302,11 +3315,11 @@ static struct srpt_port_id *srpt_wwn_to_sport_id(struct se_wwn *wwn)
>   {
>   	struct srpt_port *sport = wwn->priv;
>   
> -	if (wwn == &sport->port_guid_id.wwn)
> -		return &sport->port_guid_id;
> -	if (wwn == &sport->port_gid_id.wwn)
> -		return &sport->port_gid_id;
> -	WARN_ON_ONCE(true);
> +	BUG_ON(!sport);
> +	if (sport->guid_id && &sport->guid_id->wwn == wwn)
> +		return sport->guid_id;
> +	if (sport->gid_id && &sport->gid_id->wwn == wwn)
> +		return sport->gid_id;
>   	return NULL;
>   }
>   
> @@ -3744,6 +3757,10 @@ static struct se_portal_group *srpt_make_tpg(struct se_wwn *wwn,
>   	struct srpt_tpg *stpg;
>   	int res = -ENOMEM;
>   
> +	if (!sport_id) {
> +		pr_err("RDMA port does not exist\n");
> +		return ERR_PTR(-EINVAL);
> +	}
>   	stpg = kzalloc(sizeof(*stpg), GFP_KERNEL);
>   	if (!stpg)
>   		return ERR_PTR(res);
> @@ -3790,7 +3807,28 @@ static struct se_wwn *srpt_make_tport(struct target_fabric_configfs *tf,
>   				      struct config_group *group,
>   				      const char *name)
>   {
> -	return srpt_lookup_wwn(name) ? : ERR_PTR(-EINVAL);
> +	struct port_and_port_id papi = srpt_lookup_port(name);
> +	struct srpt_port *sport = papi.sport;
> +	struct srpt_port_id *port_id;
> +
> +	if (!papi.port_id)
> +		return ERR_PTR(-EINVAL);
> +	if (*papi.port_id)
> +		return &(*papi.port_id)->wwn;
> +	port_id = kzalloc(sizeof(*port_id), GFP_KERNEL);
> +	if (!port_id) {
> +		srpt_sdev_put(sport->sdev);
> +		return ERR_PTR(-ENOMEM);
> +	}
> +	mutex_init(&port_id->mutex);
> +	INIT_LIST_HEAD(&port_id->tpg_list);
> +	port_id->wwn.priv = sport;
> +	memcpy(port_id->name, port_id == sport->guid_id ? sport->guid_name :
> +	       sport->gid_name, ARRAY_SIZE(port_id->name));
> +
> +	*papi.port_id = port_id;
> +
> +	return &port_id->wwn;
>   }
>   
>   /**
> @@ -3799,6 +3837,17 @@ static struct se_wwn *srpt_make_tport(struct target_fabric_configfs *tf,
>    */
>   static void srpt_drop_tport(struct se_wwn *wwn)
>   {
> +	struct srpt_port_id *port_id = container_of(wwn, typeof(*port_id), wwn);
> +	struct srpt_port *sport = wwn->priv;
> +
> +	BUG_ON(!sport);
> +	if (sport->guid_id == port_id)
> +		sport->guid_id = NULL;
> +	else if (sport->gid_id == port_id)
> +		sport->gid_id = NULL;
> +
> +	srpt_sdev_put(sport->sdev);
> +	kfree(port_id);
>   }
>   
>   static ssize_t srpt_wwn_version_show(struct config_item *item, char *buf)
> diff --git a/drivers/infiniband/ulp/srpt/ib_srpt.h b/drivers/infiniband/ulp/srpt/ib_srpt.h
> index 0cb867d580f1..4c46b301eea1 100644
> --- a/drivers/infiniband/ulp/srpt/ib_srpt.h
> +++ b/drivers/infiniband/ulp/srpt/ib_srpt.h
> @@ -393,7 +393,7 @@ struct srpt_port_id {
>   };
>   
>   /**
> - * struct srpt_port - information associated by SRPT with a single IB port
> + * struct srpt_port - SRPT RDMA port information
>    * @sdev:      backpointer to the HCA information.
>    * @mad_agent: per-port management datagram processing information.
>    * @enabled:   Whether or not this target port is enabled.
> @@ -403,9 +403,9 @@ struct srpt_port_id {
>    * @gid:       cached value of the port's gid.
>    * @work:      work structure for refreshing the aforementioned cached values.
>    * @guid_name: port name in GUID format.
> - * @port_guid_id: LIO target port information for the port name in GUID format.
> + * @guid_id:   LIO target port information for the port name in GUID format.
>    * @gid_name:  port name in GID format.
> - * @port_gid_id: LIO target port information for the port name in GID format.
> + * @gid_id:    LIO target port information for the port name in GID format.
>    * @port_attrib:   Port attributes that can be accessed through configfs.
>    * @refcount:	   Number of objects associated with this port.
>    * @freed_channels: Completion that will be signaled once @refcount becomes 0.
> @@ -422,9 +422,9 @@ struct srpt_port {
>   	union ib_gid		gid;
>   	struct work_struct	work;
>   	char			guid_name[64];
> -	struct srpt_port_id	port_guid_id;
> +	struct srpt_port_id	*guid_id;
>   	char			gid_name[64];
> -	struct srpt_port_id	port_gid_id;
> +	struct srpt_port_id	*gid_id;
>   	struct srpt_port_attrib port_attrib;
>   	atomic_t		refcount;
>   	struct completion	*freed_channels;