CVE-2025-22083

In the Linux kernel, the following vulnerability has been resolved:

vhost-scsi: Fix handling of multiple calls to vhost_scsi_set_endpoint

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.