CVE-2025-22083
Publication date:
16/04/2025
In the Linux kernel, the following vulnerability has been resolved:<br />
<br />
vhost-scsi: Fix handling of multiple calls to vhost_scsi_set_endpoint<br />
<br />
If vhost_scsi_set_endpoint is called multiple times without a<br />
vhost_scsi_clear_endpoint between them, we can hit multiple bugs<br />
found by Haoran Zhang:<br />
<br />
1. Use-after-free when no tpgs are found:<br />
<br />
This fixes a use after free that occurs when vhost_scsi_set_endpoint is<br />
called more than once and calls after the first call do not find any<br />
tpgs to add to the vs_tpg. When vhost_scsi_set_endpoint first finds<br />
tpgs to add to the vs_tpg array match=true, so we will do:<br />
<br />
vhost_vq_set_backend(vq, vs_tpg);<br />
...<br />
<br />
kfree(vs->vs_tpg);<br />
vs->vs_tpg = vs_tpg;<br />
<br />
If vhost_scsi_set_endpoint is called again and no tpgs are found<br />
match=false so we skip the vhost_vq_set_backend call leaving the<br />
pointer to the vs_tpg we then free via:<br />
<br />
kfree(vs->vs_tpg);<br />
vs->vs_tpg = vs_tpg;<br />
<br />
If a scsi request is then sent we do:<br />
<br />
vhost_scsi_handle_vq -> vhost_scsi_get_req -> vhost_vq_get_backend<br />
<br />
which sees the vs_tpg we just did a kfree on.<br />
<br />
2. Tpg dir removal hang:<br />
<br />
This patch fixes an issue where we cannot remove a LIO/target layer<br />
tpg (and structs above it like the target) dir due to the refcount<br />
dropping to -1.<br />
<br />
The problem is that if vhost_scsi_set_endpoint detects a tpg is already<br />
in the vs->vs_tpg array or if the tpg has been removed so<br />
target_depend_item fails, the undepend goto handler will do<br />
target_undepend_item on all tpgs in the vs_tpg array dropping their<br />
refcount to 0. At this time vs_tpg contains both the tpgs we have added<br />
in the current vhost_scsi_set_endpoint call as well as tpgs we added in<br />
previous calls which are also in vs->vs_tpg.<br />
<br />
Later, when vhost_scsi_clear_endpoint runs it will do<br />
target_undepend_item on all the tpgs in the vs->vs_tpg which will drop<br />
their refcount to -1. Userspace will then not be able to remove the tpg<br />
and will hang when it tries to do rmdir on the tpg dir.<br />
<br />
3. Tpg leak:<br />
<br />
This fixes a bug where we can leak tpgs and cause them to be<br />
un-removable because the target name is overwritten when<br />
vhost_scsi_set_endpoint is called multiple times but with different<br />
target names.<br />
<br />
The bug occurs if a user has called VHOST_SCSI_SET_ENDPOINT and setup<br />
a vhost-scsi device to target/tpg mapping, then calls<br />
VHOST_SCSI_SET_ENDPOINT again with a new target name that has tpgs we<br />
haven&#39;t seen before (target1 has tpg1 but target2 has tpg2). When this<br />
happens we don&#39;t teardown the old target tpg mapping and just overwrite<br />
the target name and the vs->vs_tpg array. Later when we do<br />
vhost_scsi_clear_endpoint, we are passed in either target1 or target2&#39;s<br />
name and we will only match that target&#39;s tpgs when we loop over the<br />
vs->vs_tpg. We will then return from the function without doing<br />
target_undepend_item on the tpgs.<br />
<br />
Because of all these bugs, it looks like being able to call<br />
vhost_scsi_set_endpoint multiple times was never supported. The major<br />
user, QEMU, already has checks to prevent this use case. So to fix the<br />
issues, this patch prevents vhost_scsi_set_endpoint from being called<br />
if it&#39;s already successfully added tpgs. To add, remove or change the<br />
tpg config or target name, you must do a vhost_scsi_clear_endpoint<br />
first.
Severity CVSS v4.0: Pending analysis
Last modification:
06/02/2026
