On 26/05/2021 09:10, Ming Lei wrote:
When scsi_add_host_with_dma() return failure, the caller will call
scsi_host_put(shost) to release everything allocated for this host
instance. So we can't free allocated stuff in scsi_add_host_with_dma(),
otherwise double free will be caused.
Strictly speaking, these host resources allocation should have been
moved to scsi_host_alloc(), but the allocation may need driver's
info which can be built between calling scsi_host_alloc() and
scsi_add_host(), so just keep the allocations in
scsi_add_host_with_dma().
Hi Ming,
I did an experiment by making scsi_add_host_with_dma() fail by hacking
the code, like:
snprintf(shost->work_q_name, sizeof(shost->work_q_name),
"scsi_wq_%d", shost->host_no);
#if 0
shost->work_q = alloc_workqueue("%s",
WQ_SYSFS | __WQ_LEGACY | WQ_MEM_RECLAIM |
WQ_UNBOUND,
1, shost->work_q_name);
#endif
I was finding that the shost gendev kobj kref count was 2 at the "fail"
label - I would expect 1.
Did you actually ever see the release function - scsi_host_dev_release()
- being called and causing the double free?
Thanks,
John
Fixes the problem by relying on host device's release handler to
release everything.
Cc: Bart Van Assche <bvanassche@xxxxxxx>
Cc: John Garry <john.garry@xxxxxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
drivers/scsi/hosts.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)
diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index 624e2582c3df..ef8d2f512fe3 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -281,23 +281,22 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
if (!shost->work_q) {
error = -EINVAL;
- goto out_free_shost_data;
+ goto out_del_dev;
}
}
error = scsi_sysfs_add_host(shost);
if (error)
- goto out_destroy_host;
+ goto out_del_dev;
scsi_proc_host_add(shost);
scsi_autopm_put_host(shost);
return error;
- out_destroy_host:
- if (shost->work_q)
- destroy_workqueue(shost->work_q);
- out_free_shost_data:
- kfree(shost->shost_data);
+ /*
+ * any host allocation in this function will be freed in
+ * scsi_host_dev_release, so not free them in the failure path
+ */
out_del_dev:
device_del(&shost->shost_dev);
out_del_gendev:
@@ -307,7 +306,6 @@ 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;
}
