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Subject[PATCH 3.12 54/66] vhost-scsi: Take configfs group dependency during VHOST_SCSI_SET_ENDPOINT
Date
From: Nicholas Bellinger <nab@linux-iscsi.org>

3.12-stable review patch. If anyone has any objections, please let me know.

===============

commit ab8edab132829b26dd13db6caca3c242cce35dc1 upstream.

This patch addresses a bug where individual vhost-scsi configfs endpoint
groups can be removed from below while active exports to QEMU userspace
still exist, resulting in an OOPs.

It adds a configfs_depend_item() in vhost_scsi_set_endpoint() to obtain
an explicit dependency on se_tpg->tpg_group in order to prevent individual
vhost-scsi WWPN endpoints from being released via normal configfs methods
while an QEMU ioctl reference still exists.

Also, add matching configfs_undepend_item() in vhost_scsi_clear_endpoint()
to release the dependency, once QEMU's reference to the individual group
at /sys/kernel/config/target/vhost/$WWPN/$TPGT is released.

(Fix up vhost_scsi_clear_endpoint() error path - DanC)

Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
drivers/vhost/scsi.c | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index d300fd99a2b8..c5b631cceb4c 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -1194,6 +1194,7 @@ static int
vhost_scsi_set_endpoint(struct vhost_scsi *vs,
struct vhost_scsi_target *t)
{
+ struct se_portal_group *se_tpg;
struct tcm_vhost_tport *tv_tport;
struct tcm_vhost_tpg *tpg;
struct tcm_vhost_tpg **vs_tpg;
@@ -1241,6 +1242,21 @@ vhost_scsi_set_endpoint(struct vhost_scsi *vs,
ret = -EEXIST;
goto out;
}
+ /*
+ * In order to ensure individual vhost-scsi configfs
+ * groups cannot be removed while in use by vhost ioctl,
+ * go ahead and take an explicit se_tpg->tpg_group.cg_item
+ * dependency now.
+ */
+ se_tpg = &tpg->se_tpg;
+ ret = configfs_depend_item(se_tpg->se_tpg_tfo->tf_subsys,
+ &se_tpg->tpg_group.cg_item);
+ if (ret) {
+ pr_warn("configfs_depend_item() failed: %d\n", ret);
+ kfree(vs_tpg);
+ mutex_unlock(&tpg->tv_tpg_mutex);
+ goto out;
+ }
tpg->tv_tpg_vhost_count++;
tpg->vhost_scsi = vs;
vs_tpg[tpg->tport_tpgt] = tpg;
@@ -1283,6 +1299,7 @@ static int
vhost_scsi_clear_endpoint(struct vhost_scsi *vs,
struct vhost_scsi_target *t)
{
+ struct se_portal_group *se_tpg;
struct tcm_vhost_tport *tv_tport;
struct tcm_vhost_tpg *tpg;
struct vhost_virtqueue *vq;
@@ -1331,6 +1348,13 @@ vhost_scsi_clear_endpoint(struct vhost_scsi *vs,
vs->vs_tpg[target] = NULL;
match = true;
mutex_unlock(&tpg->tv_tpg_mutex);
+ /*
+ * Release se_tpg->tpg_group.cg_item configfs dependency now
+ * to allow vhost-scsi WWPN se_tpg->tpg_group shutdown to occur.
+ */
+ se_tpg = &tpg->se_tpg;
+ configfs_undepend_item(se_tpg->se_tpg_tfo->tf_subsys,
+ &se_tpg->tpg_group.cg_item);
}
if (match) {
for (i = 0; i < VHOST_SCSI_MAX_VQ; i++) {
--
2.1.3


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