CVE-2024-56544: 
Linux Kernel vulnerability analysis and mitigation

In the Linux kernel, a vulnerability (CVE-2024-56544) was discovered in the udmabuf (user-space direct memory access buffer) functionality. The issue occurs when PAGE_SIZE is 4096 and MAX_PAGE_ORDER is 10 on 64-bit machines, where page allocation only supports up to 4MB. When attempting to allocate larger buffers (e.g., 3GB), the allocation fails due to memory allocation limitations (NVD). This vulnerability affects Linux kernel versions from 4.20 up to (excluding) 6.11.11 and from 6.12 up to (excluding) 6.12.2.

The vulnerability stems from using kmalloc for array allocation in the udmabuf subsystem. Due to MAX_PAGE_ORDER limitations, kmalloc can only allocate up to 4MB (4096 * (1 << 10)) of memory. Each array entry is a pointer (8 bytes), allowing storage of up to 524,288 pages (2GB). Additionally, higher-order allocations (order 3) may fail due to memory fragmentation. The issue has been assigned a CVSS v3.1 base score of 5.5 (Medium) with vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H (NVD).

When attempting to allocate large udmabuf buffers (e.g., 3GB), the allocation fails, triggering a warning and returning NULL. This can lead to denial of service conditions in applications relying on large direct memory access buffers (NVD).

The vulnerability has been patched by changing the udmabuf array allocation from kmalloc to kvmalloc_array. This modification allows fallback to vmalloc when needed, guaranteeing allocation for any size while maintaining kmalloc allocation performance where possible (Kernel Patch).