CVE-2024-47748

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

vhost_vdpa: assign irq bypass producer token correctly

We used to call irq_bypass_unregister_producer() in vhost_vdpa_setup_vq_irq() which is problematic as we dont know if the token pointer is still valid or not.

Actually, we use the eventfd_ctx as the token so the life cycle of the token should be bound to the VHOST_SET_VRING_CALL instead of vhost_vdpa_setup_vq_irq() which could be called by set_status().

Fixing this by setting up irq bypass producers token when handling VHOST_SET_VRING_CALL and un-registering the producer before calling vhost_vring_ioctl() to prevent a possible use after free as eventfd could have been released in vhost_vring_ioctl(). And such registering and unregistering will only be done if DRIVER_OK is set.

Weakness

Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.

Affected Software

Extended Description

The use of previously-freed memory can have any number of adverse consequences, ranging from the corruption of valid data to the execution of arbitrary code, depending on the instantiation and timing of the flaw. The simplest way data corruption may occur involves the system’s reuse of the freed memory. Use-after-free errors have two common and sometimes overlapping causes:

In this scenario, the memory in question is allocated to another pointer validly at some point after it has been freed. The original pointer to the freed memory is used again and points to somewhere within the new allocation. As the data is changed, it corrupts the validly used memory; this induces undefined behavior in the process. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.

Potential Mitigations

References

• https://git.kernel.org/stable/c/02e9e9366fefe461719da5d173385b6685f70319
• https://git.kernel.org/stable/c/0c170b1e918b9afac25e2bbd01eaa2bfc0ece8c0
• https://git.kernel.org/stable/c/7cf2fb51175cafe01df8c43fa15a06194a59c6e2
• https://git.kernel.org/stable/c/927a2580208e0f9b0b47b08f1c802b7233a7ba3c
• https://git.kernel.org/stable/c/ca64edd7ae93402af2596a952e0d94d545e2b9c0
• https://git.kernel.org/stable/c/ec5f1b54ceb23475049ada6e7a43452cf4df88d1
• https://git.kernel.org/stable/c/fae9b1776f53aab93ab345bdbf653b991aed717d