Subject: CVE-2024-26698: hv_netvsc: Fix race condition between netvsc_probe and netvsc_remove

From: Greg Kroah-Hartman <[email-masked]>

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

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

hv_netvsc: Fix race condition between netvsc_probe and netvsc_remove

In commit ac5047671758 ("hv_netvsc: Disable NAPI before closing the
VMBus channel"), napi_disable was getting called for all channels,
including all subchannels without confirming if they are enabled or not.

This caused hv_netvsc getting hung at napi_disable, when netvsc_probe()
has finished running but nvdev->subchan_work has not started yet.
netvsc_subchan_work() -> rndis_set_subchannel() has not created the
sub-channels and because of that netvsc_sc_open() is not running.
netvsc_remove() calls cancel_work_sync(&nvdev->subchan_work), for which
netvsc_subchan_work did not run.

netif_napi_add() sets the bit NAPI_STATE_SCHED because it ensures NAPI
cannot be scheduled. Then netvsc_sc_open() -> napi_enable will clear the
NAPIF_STATE_SCHED bit, so it can be scheduled. napi_disable() does the
opposite.

Now during netvsc_device_remove(), when napi_disable is called for those
subchannels, napi_disable gets stuck on infinite msleep.

This fix addresses this problem by ensuring that napi_disable() is not
getting called for non-enabled NAPI struct.
But netif_napi_del() is still necessary for these non-enabled NAPI struct
for cleanup purpose.

Call trace:
[  654.559417] task:modprobe        state:D stack:    0 pid: 2321 ppid:  1091 flags:0x00004002
[  654.568030] Call Trace:
[  654.571221]  <TASK>
[  654.573790]  __schedule+0x2d6/0x960
[  654.577733]  schedule+0x69/0xf0
[  654.581214]  schedule_timeout+0x87/0x140
[  654.585463]  ? __bpf_trace_tick_stop+0x20/0x20
[  654.590291]  msleep+0x2d/0x40
[  654.593625]  napi_disable+0x2b/0x80
[  654.597437]  netvsc_device_remove+0x8a/0x1f0 [hv_netvsc]
[  654.603935]  rndis_filter_device_remove+0x194/0x1c0 [hv_netvsc]
[  654.611101]  ? do_wait_intr+0xb0/0xb0
[  654.615753]  netvsc_remove+0x7c/0x120 [hv_netvsc]
[  654.621675]  vmbus_remove+0x27/0x40 [hv_vmbus]

The Linux kernel CVE team has assigned CVE-2024-26698 to this issue.

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

	Issue introduced in 5.8 with commit ac5047671758 and fixed in 5.10.210 with commit 9ec807e7b6f5
	Issue introduced in 5.8 with commit ac5047671758 and fixed in 5.15.149 with commit 7656372ae190
	Issue introduced in 5.8 with commit ac5047671758 and fixed in 6.1.79 with commit 48a8ccccffba
	Issue introduced in 5.8 with commit ac5047671758 and fixed in 6.6.18 with commit 22a77c0f5b82
	Issue introduced in 5.8 with commit ac5047671758 and fixed in 6.7.6 with commit 0e8875de9dad
	Issue introduced in 5.8 with commit ac5047671758 and fixed in 6.8 with commit e0526ec5360a

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-2024-26698
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/net/hyperv/netvsc.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/9ec807e7b6f5fcf9499f3baa69f254bb239a847f
	https://git.kernel.org/stable/c/7656372ae190e54e8c8cf1039725a5ea59fdf84a
	https://git.kernel.org/stable/c/48a8ccccffbae10c91d31fc872db5c31aba07518
	https://git.kernel.org/stable/c/22a77c0f5b8233237731df3288d067af51a2fd7b
	https://git.kernel.org/stable/c/0e8875de9dad12805ff66e92cd5edea6a421f1cd
	https://git.kernel.org/stable/c/e0526ec5360a48ad3ab2e26e802b0532302a7e11