Message-ID: <2025041614-CVE-2025-22083-8012@gregkh>
Date: Wed, 16 Apr 2025 16:12:54 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2025-22083: vhost-scsi: Fix handling of multiple calls to vhost_scsi_set_endpoint

Description
===========

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.

The Linux kernel CVE team has assigned CVE-2025-22083 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 3.9 with commit 4f7f46d32c9875004fae1d57ae3c02cc2e6cd6a3 and fixed in 6.6.87 with commit 2b34bdc42df047794542f3e220fe989124e4499a
	Issue introduced in 3.9 with commit 4f7f46d32c9875004fae1d57ae3c02cc2e6cd6a3 and fixed in 6.12.23 with commit 3a19eb3d9818e28f14c818a18dc913344a52ca92
	Issue introduced in 3.9 with commit 4f7f46d32c9875004fae1d57ae3c02cc2e6cd6a3 and fixed in 6.13.11 with commit 3fd054baf382a426bbf5135ede0fc5673db74d3e
	Issue introduced in 3.9 with commit 4f7f46d32c9875004fae1d57ae3c02cc2e6cd6a3 and fixed in 6.14.2 with commit 63b449f73ab0dcc0ba11ceaa4c5c70bc86ccf03c
	Issue introduced in 3.9 with commit 4f7f46d32c9875004fae1d57ae3c02cc2e6cd6a3 and fixed in 6.15-rc1 with commit 5dd639a1646ef5fe8f4bf270fad47c5c3755b9b6

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2025-22083
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/vhost/scsi.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/2b34bdc42df047794542f3e220fe989124e4499a
	https://git.kernel.org/stable/c/3a19eb3d9818e28f14c818a18dc913344a52ca92
	https://git.kernel.org/stable/c/3fd054baf382a426bbf5135ede0fc5673db74d3e
	https://git.kernel.org/stable/c/63b449f73ab0dcc0ba11ceaa4c5c70bc86ccf03c
	https://git.kernel.org/stable/c/5dd639a1646ef5fe8f4bf270fad47c5c3755b9b6

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