CVE-2024-57798

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

drm/dp_mst: Ensure mst_primary pointer is valid in drm_dp_mst_handle_up_req()

While receiving an MST up request message from one thread in drm_dp_mst_handle_up_req(), the MST topology could be removed from another thread via drm_dp_mst_topology_mgr_set_mst(false), freeing mst_primary and setting drm_dp_mst_topology_mgr::mst_primary to NULL. This could lead to a NULL deref/use-after-free of mst_primary in drm_dp_mst_handle_up_req().

Avoid the above by holding a reference for mst_primary in drm_dp_mst_handle_up_req() while its used.

v2: Fix kfreeing the request if getting an mst_primary reference fails.

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/9735d40f5fde9970aa46e828ecc85c32571d58a2
• https://git.kernel.org/stable/c/ce55818b2d3a999f886af91679589e4644ff1dc8
• https://git.kernel.org/stable/c/e54b00086f7473dbda1a7d6fc47720ced157c6a8
• https://git.kernel.org/stable/c/f61b2e5e7821f868d6afc22382a66a30ee780ba0