[PATCH 5.19 020/207] scsi: core: Fix a use-after-free

Greg Kroah-Hartman
2022-09-26T11:39:32Z

From: Bart Van Assche <bvanassche@acm.org>

[ Upstream commit 8fe4ce5836e932f5766317cb651c1ff2a4cd0506 ]

There are two .exit_cmd_priv implementations. Both implementations use
resources associated with the SCSI host. Make sure that these resources are
still available when .exit_cmd_priv is called by waiting inside
scsi_remove_host() until the tag set has been freed.

This commit fixes the following use-after-free:

==================================================================
BUG: KASAN: use-after-free in srp_exit_cmd_priv+0x27/0xd0 [ib_srp]
Read of size 8 at addr ffff888100337000 by task multipathd/16727
Call Trace:
<TASK>
dump_stack_lvl+0x34/0x44
print_report.cold+0x5e/0x5db
kasan_report+0xab/0x120
srp_exit_cmd_priv+0x27/0xd0 [ib_srp]
scsi_mq_exit_request+0x4d/0x70
blk_mq_free_rqs+0x143/0x410
__blk_mq_free_map_and_rqs+0x6e/0x100
blk_mq_free_tag_set+0x2b/0x160
scsi_host_dev_release+0xf3/0x1a0
device_release+0x54/0xe0
kobject_put+0xa5/0x120
device_release+0x54/0xe0
kobject_put+0xa5/0x120
scsi_device_dev_release_usercontext+0x4c1/0x4e0
execute_in_process_context+0x23/0x90
device_release+0x54/0xe0
kobject_put+0xa5/0x120
scsi_disk_release+0x3f/0x50
device_release+0x54/0xe0
kobject_put+0xa5/0x120
disk_release+0x17f/0x1b0
device_release+0x54/0xe0
kobject_put+0xa5/0x120
dm_put_table_device+0xa3/0x160 [dm_mod]
dm_put_device+0xd0/0x140 [dm_mod]
free_priority_group+0xd8/0x110 [dm_multipath]
free_multipath+0x94/0xe0 [dm_multipath]
dm_table_destroy+0xa2/0x1e0 [dm_mod]
__dm_destroy+0x196/0x350 [dm_mod]
dev_remove+0x10c/0x160 [dm_mod]
ctl_ioctl+0x2c2/0x590 [dm_mod]
dm_ctl_ioctl+0x5/0x10 [dm_mod]
__x64_sys_ioctl+0xb4/0xf0
dm_ctl_ioctl+0x5/0x10 [dm_mod]
__x64_sys_ioctl+0xb4/0xf0
do_syscall_64+0x3b/0x90
entry_SYSCALL_64_after_hwframe+0x46/0xb0

Link: https://lore.kernel.org/r/20220826002635.919423-1-bvanassche@acm.org
Fixes: 65ca846a5314 ("scsi: core: Introduce {init,exit}_cmd_priv()")
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Mike Christie <michael.christie@oracle.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: John Garry <john.garry@huawei.com>
Cc: Li Zhijian <lizhijian@fujitsu.com>
Reported-by: Li Zhijian <lizhijian@fujitsu.com>
Tested-by: Li Zhijian <lizhijian@fujitsu.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/scsi/hosts.c | 16 +++++++++++++---
drivers/scsi/scsi_lib.c | 6 +++++-
drivers/scsi/scsi_priv.h | 2 +-
drivers/scsi/scsi_scan.c | 1 +
drivers/scsi/scsi_sysfs.c | 1 +
include/scsi/scsi_host.h | 2 ++
6 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index 8352f90d997d..ae9a107c520d 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -182,6 +182,15 @@ void scsi_remove_host(struct Scsi_Host *shost)
mutex_unlock(&shost->scan_mutex);
scsi_proc_host_rm(shost);

+ /*
+ * New SCSI devices cannot be attached anymore because of the SCSI host
+ * state so drop the tag set refcnt. Wait until the tag set refcnt drops
+ * to zero because .exit_cmd_priv implementations may need the host
+ * pointer.
+ */
+ kref_put(&shost->tagset_refcnt, scsi_mq_free_tags);
+ wait_for_completion(&shost->tagset_freed);
+
spin_lock_irqsave(shost->host_lock, flags);
if (scsi_host_set_state(shost, SHOST_DEL))
BUG_ON(scsi_host_set_state(shost, SHOST_DEL_RECOVERY));
@@ -240,6 +249,9 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
if (error)
goto fail;

+ kref_init(&shost->tagset_refcnt);
+ init_completion(&shost->tagset_freed);
+
/*
* Increase usage count temporarily here so that calling
* scsi_autopm_put_host() will trigger runtime idle if there is
@@ -312,6 +324,7 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
pm_runtime_disable(&shost->shost_gendev);
pm_runtime_set_suspended(&shost->shost_gendev);
pm_runtime_put_noidle(&shost->shost_gendev);
+ kref_put(&shost->tagset_refcnt, scsi_mq_free_tags);
fail:
return error;
}
@@ -345,9 +358,6 @@ static void scsi_host_dev_release(struct device *dev)
kfree(dev_name(&shost->shost_dev));
}

- if (shost->tag_set.tags)
- scsi_mq_destroy_tags(shost);
-
kfree(shost->shost_data);

ida_simple_remove(&host_index_ida, shost->host_no);
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 0a267d6e2f7c..7e990f7a9f16 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1995,9 +1995,13 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost)
return blk_mq_alloc_tag_set(tag_set);
}

-void scsi_mq_destroy_tags(struct Scsi_Host *shost)
+void scsi_mq_free_tags(struct kref *kref)
{
+ struct Scsi_Host *shost = container_of(kref, typeof(*shost),
+ tagset_refcnt);
+
blk_mq_free_tag_set(&shost->tag_set);
+ complete(&shost->tagset_freed);
}

/**
diff --git a/drivers/scsi/scsi_priv.h b/drivers/scsi/scsi_priv.h
index 5c4786310a31..a0ee31d55f5f 100644
--- a/drivers/scsi/scsi_priv.h
+++ b/drivers/scsi/scsi_priv.h
@@ -94,7 +94,7 @@ extern void scsi_run_host_queues(struct Scsi_Host *shost);
extern void scsi_requeue_run_queue(struct work_struct *work);
extern void scsi_start_queue(struct scsi_device *sdev);
extern int scsi_mq_setup_tags(struct Scsi_Host *shost);
-extern void scsi_mq_destroy_tags(struct Scsi_Host *shost);
+extern void scsi_mq_free_tags(struct kref *kref);
extern void scsi_exit_queue(void);
extern void scsi_evt_thread(struct work_struct *work);

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 91ac901a6682..5d27f5196de6 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -340,6 +340,7 @@ static struct scsi_device *scsi_alloc_sdev(struct scsi_target *starget,
kfree(sdev);
goto out;
}
+ kref_get(&sdev->host->tagset_refcnt);
sdev->request_queue = q;
q->queuedata = sdev;
__scsi_init_queue(sdev->host, q);
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index aa70d9282161..5d61f58399dc 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -1476,6 +1476,7 @@ void __scsi_remove_device(struct scsi_device *sdev)
mutex_unlock(&sdev->state_mutex);

blk_mq_destroy_queue(sdev->request_queue);
+ kref_put(&sdev->host->tagset_refcnt, scsi_mq_free_tags);
cancel_work_sync(&sdev->requeue_work);

if (sdev->host->hostt->slave_destroy)
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index 667d889b92b5..3e1cea155049 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -557,6 +557,8 @@ struct Scsi_Host {
struct scsi_host_template *hostt;
struct scsi_transport_template *transportt;

+ struct kref tagset_refcnt;
+ struct completion tagset_freed;
/* Area to keep a shared tag map */
struct blk_mq_tag_set tag_set;

--
2.35.1