6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Mike Christie michael.christie@oracle.com
[ Upstream commit 5dd639a1646ef5fe8f4bf270fad47c5c3755b9b6 ]
If vhost_scsi_set_endpoint is called multiple times without a vhost_scsi_clear_endpoint between them, we can hit multiple bugs found by Haoran Zhang:
1. Use-after-free when no tpgs are found:
This fixes a use after free that occurs when vhost_scsi_set_endpoint is called more than once and calls after the first call do not find any tpgs to add to the vs_tpg. When vhost_scsi_set_endpoint first finds tpgs to add to the vs_tpg array match=true, so we will do:
vhost_vq_set_backend(vq, vs_tpg); ...
kfree(vs->vs_tpg); vs->vs_tpg = vs_tpg;
If vhost_scsi_set_endpoint is called again and no tpgs are found match=false so we skip the vhost_vq_set_backend call leaving the pointer to the vs_tpg we then free via:
kfree(vs->vs_tpg); vs->vs_tpg = vs_tpg;
If a scsi request is then sent we do:
vhost_scsi_handle_vq -> vhost_scsi_get_req -> vhost_vq_get_backend
which sees the vs_tpg we just did a kfree on.
2. Tpg dir removal hang:
This patch fixes an issue where we cannot remove a LIO/target layer tpg (and structs above it like the target) dir due to the refcount dropping to -1.
The problem is that if vhost_scsi_set_endpoint detects a tpg is already in the vs->vs_tpg array or if the tpg has been removed so target_depend_item fails, the undepend goto handler will do target_undepend_item on all tpgs in the vs_tpg array dropping their refcount to 0. At this time vs_tpg contains both the tpgs we have added in the current vhost_scsi_set_endpoint call as well as tpgs we added in previous calls which are also in vs->vs_tpg.
Later, when vhost_scsi_clear_endpoint runs it will do target_undepend_item on all the tpgs in the vs->vs_tpg which will drop their refcount to -1. Userspace will then not be able to remove the tpg and will hang when it tries to do rmdir on the tpg dir.
3. Tpg leak:
This fixes a bug where we can leak tpgs and cause them to be un-removable because the target name is overwritten when vhost_scsi_set_endpoint is called multiple times but with different target names.
The bug occurs if a user has called VHOST_SCSI_SET_ENDPOINT and setup a vhost-scsi device to target/tpg mapping, then calls VHOST_SCSI_SET_ENDPOINT again with a new target name that has tpgs we haven't seen before (target1 has tpg1 but target2 has tpg2). When this happens we don't teardown the old target tpg mapping and just overwrite the target name and the vs->vs_tpg array. Later when we do vhost_scsi_clear_endpoint, we are passed in either target1 or target2's name and we will only match that target's tpgs when we loop over the vs->vs_tpg. We will then return from the function without doing target_undepend_item on the tpgs.
Because of all these bugs, it looks like being able to call vhost_scsi_set_endpoint multiple times was never supported. The major user, QEMU, already has checks to prevent this use case. So to fix the issues, this patch prevents vhost_scsi_set_endpoint from being called if it's already successfully added tpgs. To add, remove or change the tpg config or target name, you must do a vhost_scsi_clear_endpoint first.
Fixes: 25b98b64e284 ("vhost scsi: alloc cmds per vq instead of session") Fixes: 4f7f46d32c98 ("tcm_vhost: Use vq->private_data to indicate if the endpoint is setup") Reported-by: Haoran Zhang wh1sper@zju.edu.cn Closes: https://lore.kernel.org/virtualization/e418a5ee-45ca-4d18-9b5d-6f8b6b1add8e@... Signed-off-by: Mike Christie michael.christie@oracle.com Reviewed-by: Stefan Hajnoczi stefanha@redhat.com Message-Id: 20250129210922.121533-1-michael.christie@oracle.com Signed-off-by: Michael S. Tsirkin mst@redhat.com Acked-by: Stefano Garzarella sgarzare@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/vhost/scsi.c | 25 +++++++++++++------------ 1 file changed, 13 insertions(+), 12 deletions(-)
diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c index 99813232c25e9..8d8a22504d71f 100644 --- a/drivers/vhost/scsi.c +++ b/drivers/vhost/scsi.c @@ -1688,14 +1688,19 @@ vhost_scsi_set_endpoint(struct vhost_scsi *vs, } }
+ if (vs->vs_tpg) { + pr_err("vhost-scsi endpoint already set for %s.\n", + vs->vs_vhost_wwpn); + ret = -EEXIST; + goto out; + } + len = sizeof(vs_tpg[0]) * VHOST_SCSI_MAX_TARGET; vs_tpg = kzalloc(len, GFP_KERNEL); if (!vs_tpg) { ret = -ENOMEM; goto out; } - if (vs->vs_tpg) - memcpy(vs_tpg, vs->vs_tpg, len);
mutex_lock(&vhost_scsi_mutex); list_for_each_entry(tpg, &vhost_scsi_list, tv_tpg_list) { @@ -1711,12 +1716,6 @@ vhost_scsi_set_endpoint(struct vhost_scsi *vs, tv_tport = tpg->tport;
if (!strcmp(tv_tport->tport_name, t->vhost_wwpn)) { - if (vs->vs_tpg && vs->vs_tpg[tpg->tport_tpgt]) { - mutex_unlock(&tpg->tv_tpg_mutex); - mutex_unlock(&vhost_scsi_mutex); - ret = -EEXIST; - goto undepend; - } /* * In order to ensure individual vhost-scsi configfs * groups cannot be removed while in use by vhost ioctl, @@ -1763,15 +1762,15 @@ vhost_scsi_set_endpoint(struct vhost_scsi *vs, } ret = 0; } else { - ret = -EEXIST; + ret = -ENODEV; + goto free_tpg; }
/* - * Act as synchronize_rcu to make sure access to - * old vs->vs_tpg is finished. + * Act as synchronize_rcu to make sure requests after this point + * see a fully setup device. */ vhost_scsi_flush(vs); - kfree(vs->vs_tpg); vs->vs_tpg = vs_tpg; goto out;
@@ -1791,6 +1790,7 @@ vhost_scsi_set_endpoint(struct vhost_scsi *vs, target_undepend_item(&tpg->se_tpg.tpg_group.cg_item); } } +free_tpg: kfree(vs_tpg); out: mutex_unlock(&vs->dev.mutex); @@ -1893,6 +1893,7 @@ vhost_scsi_clear_endpoint(struct vhost_scsi *vs, vhost_scsi_flush(vs); kfree(vs->vs_tpg); vs->vs_tpg = NULL; + memset(vs->vs_vhost_wwpn, 0, sizeof(vs->vs_vhost_wwpn)); WARN_ON(vs->vs_events_nr); mutex_unlock(&vs->dev.mutex); return 0;