[PATCH v2 3/3] scsi: core: Call blk_mq_free_tag_set() earlier

Bart Van Assche
2022-06-30T21:37:50Z

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 moving the .exit_cmd_priv
calls from scsi_host_dev_release() to scsi_forget_host(). Moving
blk_mq_free_tag_set() from scsi_host_dev_release() to scsi_forget_host() is
safe because scsi_forget_host() drains all the request queues that use the
host tag set. This guarantees that no requests are in flight and also that
no new requests will be allocated from the host tag set.

This patch 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

Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.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>
Fixes: 65ca846a5314 ("scsi: core: Introduce {init,exit}_cmd_priv()")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
drivers/scsi/hosts.c | 10 +++++-----
drivers/scsi/scsi_lib.c | 3 +++
2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index ef6c0e37acce..74bfa187fe19 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -182,6 +182,8 @@ void scsi_remove_host(struct Scsi_Host *shost)
mutex_unlock(&shost->scan_mutex);
scsi_proc_host_rm(shost);

+ scsi_mq_destroy_tags(shost);
+
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));
@@ -295,8 +297,8 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
return error;

/*
- * Any host allocation in this function will be freed in
- * scsi_host_dev_release().
+ * Any resources associated with the SCSI host in this function except
+ * the tag set will be freed by scsi_host_dev_release().
*/
out_del_dev:
device_del(&shost->shost_dev);
@@ -312,6 +314,7 @@ 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);
+ scsi_mq_destroy_tags(shost);
fail:
return error;
}
@@ -345,9 +348,6 @@ 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_free(&host_index_ida, shost->host_no);
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 6ffc9e4258a8..1aa1a279f8f3 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1990,7 +1990,10 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost)

void scsi_mq_destroy_tags(struct Scsi_Host *shost)
{
+ if (!shost->tag_set.tags)
+ return;
blk_mq_free_tag_set(&shost->tag_set);
+ WARN_ON_ONCE(shost->tag_set.tags);
}

/**