CVE-2024-56652

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

drm/xe/reg_sr: Remove register pool

That pool implementation doesnt really work: if the krealloc happens to move the memory and return another address, the entries in the xarray become invalid, leading to use-after-free later:

BUG: KASAN: slab-use-after-free in xe_reg_sr_apply_mmio+0x570/0x760 [xe]
Read of size 4 at addr ffff8881244b2590 by task modprobe/2753

Allocated by task 2753:
 kasan_save_stack+0x39/0x70
 kasan_save_track+0x14/0x40
 kasan_save_alloc_info+0x37/0x60
 __kasan_kmalloc+0xc3/0xd0
 __kmalloc_node_track_caller_noprof+0x200/0x6d0
 krealloc_noprof+0x229/0x380

Simplify the code to fix the bug. A better pooling strategy may be added back later if needed.

(cherry picked from commit e5283bd4dfecbd3335f43b62a68e24dae23f59e4)

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/b0193a31a0ca5a0f9e60bb4a86537d46b98111b8
• https://git.kernel.org/stable/c/d7b028656c29b22fcde1c6ee1df5b28fbba987b5