Vulnerability CVE-2024-26813
Published: 2024-04-05

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

vfio/platform: Create persistent IRQ handlers

The vfio-platform SET_IRQS ioctl currently allows loopback triggering of
an interrupt before a signaling eventfd has been configured by the user,
which thereby allows a NULL pointer dereference.

Rather than register the IRQ relative to a valid trigger, register all
IRQs in a disabled state in the device open path. This allows mask
operations on the IRQ to nest within the overall enable state governed
by a valid eventfd signal. This decouples @masked, protected by the
@locked spinlock from @trigger, protected via the @igate mutex.

In doing so, it's guaranteed that changes to @trigger cannot race the
IRQ handlers because the IRQ handler is synchronously disabled before
modifying the trigger, and loopback triggering of the IRQ via ioctl is
safe due to serialization with trigger changes via igate.

For compatibility, request_irq() failures are maintained to be local to
the SET_IRQS ioctl rather than a fatal error in the open device path.
This allows, for example, a userspace driver with polling mode support
to continue to work regardless of moving the request_irq() call site.
This necessarily blocks all SET_IRQS access to the failed index.

 References:
https://git.kernel.org/stable/c/7932db06c82c5b2f42a4d1a849d97dba9ce4a362
https://git.kernel.org/stable/c/62d4e43a569b67929eb3319780be5359694c8086
https://git.kernel.org/stable/c/d6bedd6acc0bcb1e7e010bc046032e47f08d379f
https://git.kernel.org/stable/c/0f8d8f9c2173a541812dd750529f4a415117eb29
https://git.kernel.org/stable/c/675daf435e9f8e5a5eab140a9864dfad6668b375
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