In the Linux kernel, the following vulnerability has been resolved:
Drivers: hv: util: Avoid accessing a ringbuffer not initialized yet
If the KVP (or VSS) daemon starts before the VMBus channel's ringbuffer is
fully initialized, we can hit the panic below:
hv_utils: Registering HyperV Utility Driver
hv_vmbus: registering driver hv_utils
...
BUG: kernel NULL pointer dereference, address: 0000000000000000
CPU: 44 UID: 0 PID: 2552 Comm: hv_kvp_daemon Tainted: G E 6.11.0-rc3+ #1
RIP: 0010:hv_pkt_iter_first+0x12/0xd0
Call Trace:
...
vmbus_recvpacket
hv_kvp_onchannelcallback
vmbus_on_event
tasklet_action_common
tasklet_action
handle_softirqs
irq_exit_rcu
sysvec_hyperv_stimer0
</IRQ>
<TASK>
asm_sysvec_hyperv_stimer0
...
kvp_register_done
hvt_op_read
vfs_read
ksys_read
__x64_sys_read
This can happen because the KVP/VSS channel callback can be invoked
even before the channel is fully opened:
1) as soon as hv_kvp_init() -> hvutil_transport_init() creates
/dev/vmbus/hv_kvp, the kvp daemon can open the device file immediately and
register itself to the driver by writing a message KVP_OP_REGISTER1 to the
file (which is handled by kvp_on_msg() ->kvp_handle_handshake()) and
reading the file for the driver's response, which is handled by
hvt_op_read(), which calls hvt->on_read(), i.e. kvp_register_done().
2) the problem with kvp_register_done() is that it can cause the
channel callback to be called even before the channel is fully opened,
and when the channel callback is starting to run, util_probe()->
vmbus_open() may have not initialized the ringbuffer yet, so the
callback can hit the panic of NULL pointer dereference.
To reproduce the panic consistently, we can add a "ssleep(10)" for KVP in
__vmbus_open(), just before the first hv_ringbuffer_init(), and then we
unload and reload the driver hv_utils, and run the daemon manually within
the 10 seconds.
Fix the panic by reordering the steps in util_probe() so the char dev
entry used by the KVP or VSS daemon is not created until after
vmbus_open() has completed. This reordering prevents the race condition
from happening.
Metrics
Affected Vendors & Products
| Vendors | Products |
|---|---|
| Linux |
|
Configuration 1 [-]
|
No data.
References
History
Tue, 04 Nov 2025 09:15:00 +0000
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ssvc
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Mon, 03 Nov 2025 21:30:00 +0000
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Thu, 16 Jan 2025 15:45:00 +0000
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| First Time appeared |
Linux
Linux linux Kernel |
|
| Weaknesses | CWE-476 | |
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.13:rc1:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.13:rc2:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.13:rc3:*:*:*:*:*:* |
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| Vendors & Products |
Linux
Linux linux Kernel |
Tue, 14 Jan 2025 08:45:00 +0000
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| Metrics |
threat_severity
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cvssV3_1
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Sat, 11 Jan 2025 12:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: Drivers: hv: util: Avoid accessing a ringbuffer not initialized yet If the KVP (or VSS) daemon starts before the VMBus channel's ringbuffer is fully initialized, we can hit the panic below: hv_utils: Registering HyperV Utility Driver hv_vmbus: registering driver hv_utils ... BUG: kernel NULL pointer dereference, address: 0000000000000000 CPU: 44 UID: 0 PID: 2552 Comm: hv_kvp_daemon Tainted: G E 6.11.0-rc3+ #1 RIP: 0010:hv_pkt_iter_first+0x12/0xd0 Call Trace: ... vmbus_recvpacket hv_kvp_onchannelcallback vmbus_on_event tasklet_action_common tasklet_action handle_softirqs irq_exit_rcu sysvec_hyperv_stimer0 </IRQ> <TASK> asm_sysvec_hyperv_stimer0 ... kvp_register_done hvt_op_read vfs_read ksys_read __x64_sys_read This can happen because the KVP/VSS channel callback can be invoked even before the channel is fully opened: 1) as soon as hv_kvp_init() -> hvutil_transport_init() creates /dev/vmbus/hv_kvp, the kvp daemon can open the device file immediately and register itself to the driver by writing a message KVP_OP_REGISTER1 to the file (which is handled by kvp_on_msg() ->kvp_handle_handshake()) and reading the file for the driver's response, which is handled by hvt_op_read(), which calls hvt->on_read(), i.e. kvp_register_done(). 2) the problem with kvp_register_done() is that it can cause the channel callback to be called even before the channel is fully opened, and when the channel callback is starting to run, util_probe()-> vmbus_open() may have not initialized the ringbuffer yet, so the callback can hit the panic of NULL pointer dereference. To reproduce the panic consistently, we can add a "ssleep(10)" for KVP in __vmbus_open(), just before the first hv_ringbuffer_init(), and then we unload and reload the driver hv_utils, and run the daemon manually within the 10 seconds. Fix the panic by reordering the steps in util_probe() so the char dev entry used by the KVP or VSS daemon is not created until after vmbus_open() has completed. This reordering prevents the race condition from happening. | |
| Title | Drivers: hv: util: Avoid accessing a ringbuffer not initialized yet | |
| References |
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MITRE
Status: PUBLISHED
Assigner: Linux
Published: 2025-01-11T12:35:44.800Z
Updated: 2025-11-03T20:48:52.286Z
Reserved: 2025-01-09T09:49:29.678Z
Link: CVE-2024-55916
Vulnrichment
Updated: 2025-11-03T20:48:52.286Z
NVD
Status : Modified
Published: 2025-01-11T13:15:28.353
Modified: 2025-11-03T21:17:50.523
Link: CVE-2024-55916
Redhat