Race Condition Affecting kernel-rt-devel package, versions *

Note: Versions mentioned in the description apply only to the upstream kernel-rt-devel package and not the kernel-rt-devel package as distributed by Centos. See How to fix? for Centos:8 relevant fixed versions and status.

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]

• https://access.redhat.com/security/cve/CVE-2024-26698
• https://git.kernel.org/stable/c/0e8875de9dad12805ff66e92cd5edea6a421f1cd
• https://git.kernel.org/stable/c/22a77c0f5b8233237731df3288d067af51a2fd7b
• https://git.kernel.org/stable/c/48a8ccccffbae10c91d31fc872db5c31aba07518
• https://git.kernel.org/stable/c/7656372ae190e54e8c8cf1039725a5ea59fdf84a
• https://git.kernel.org/stable/c/9ec807e7b6f5fcf9499f3baa69f254bb239a847f
• https://git.kernel.org/stable/c/e0526ec5360a48ad3ab2e26e802b0532302a7e11
• https://lists.debian.org/debian-lts-announce/2024/06/msg00017.html