CVE-2025-40048
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-10-28

Last updated on: 2025-10-30

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: uio_hv_generic: Let userspace take care of interrupt mask Remove the logic to set interrupt mask by default in uio_hv_generic driver as the interrupt mask value is supposed to be controlled completely by the user space. If the mask bit gets changed by the driver, concurrently with user mode operating on the ring, the mask bit may be set when it is supposed to be clear, and the user-mode driver will miss an interrupt which will cause a hang. For eg- when the driver sets inbound ring buffer interrupt mask to 1, the host does not interrupt the guest on the UIO VMBus channel. However, setting the mask does not prevent the host from putting a message in the inbound ring buffer. So let’s assume that happens, the host puts a message into the ring buffer but does not interrupt. Subsequently, the user space code in the guest sets the inbound ring buffer interrupt mask to 0, saying “Hey, I’m ready for interrupts”. User space code then calls pread() to wait for an interrupt. Then one of two things happens: * The host never sends another message. So the pread() waits forever. * The host does send another message. But because there’s already a message in the ring buffer, it doesn’t generate an interrupt. This is the correct behavior, because the host should only send an interrupt when the inbound ring buffer transitions from empty to not-empty. Adding an additional message to a ring buffer that is not empty is not supposed to generate an interrupt on the guest. Since the guest is waiting in pread() and not removing messages from the ring buffer, the pread() waits forever. This could be easily reproduced in hv_fcopy_uio_daemon if we delay setting interrupt mask to 0. Similarly if hv_uio_channel_cb() sets the interrupt_mask to 1, there’s a race condition. Once user space empties the inbound ring buffer, but before user space sets interrupt_mask to 0, the host could put another message in the ring buffer but it wouldn’t interrupt. Then the next pread() would hang. Fix these by removing all instances where interrupt_mask is changed, while keeping the one in set_event() unchanged to enable userspace control the interrupt mask by writing 0/1 to /dev/uioX.
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Meta Information
Published
2025-10-28
Last Modified
2025-10-30
Generated
2026-05-07
AI Q&A
2025-10-28
EPSS Evaluated
2026-05-05
NVD
CVE-2025-40048
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-UNKNOWN
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability involves the uio_hv_generic driver in the Linux kernel improperly managing the interrupt mask. The driver was setting the interrupt mask by default, but this should be controlled entirely by user space. If the driver changes the mask concurrently with user space operations, it can cause the mask bit to be set incorrectly, leading the user-mode driver to miss interrupts. This results in the user space process waiting indefinitely (hanging) because it either never receives an interrupt or misses an interrupt due to a race condition where messages in the ring buffer do not trigger interrupts as expected.


How can this vulnerability impact me? :

This vulnerability can cause user space processes that rely on interrupts from the uio_hv_generic driver to hang indefinitely. Specifically, if interrupts are missed due to improper interrupt mask handling, processes waiting for these interrupts (e.g., via pread()) may never resume, leading to system hangs or degraded functionality in applications relying on these interrupts.


What immediate steps should I take to mitigate this vulnerability?

To mitigate this vulnerability, ensure that the uio_hv_generic driver does not change the interrupt mask by itself and that userspace controls the interrupt mask by writing 0 or 1 to /dev/uioX. Avoid any driver logic that sets the interrupt mask automatically. Applying the patch or update that removes the logic to set the interrupt mask by default in the uio_hv_generic driver is recommended.


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