CVE-2024-58099

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

vmxnet3: Fix packet corruption in vmxnet3_xdp_xmit_frame

Andrew and Nikolay reported connectivity issues with Ciliums service load-balancing in case of vmxnet3.

If a BPF program for native XDP adds an encapsulation header such as IPIP and transmits the packet out the same interface, then in case of vmxnet3 a corrupted packet is being sent and subsequently dropped on the path.

vmxnet3_xdp_xmit_frame() which is called e.g. via vmxnet3_run_xdp() through vmxnet3_xdp_xmit_back() calculates an incorrect DMA address:

page = virt_to_page(xdpf->data); tbi->dma_addr = page_pool_get_dma_addr(page) + VMXNET3_XDP_HEADROOM; dma_sync_single_for_device(&adapter->pdev->dev, tbi->dma_addr, buf_size, DMA_TO_DEVICE);

The above assumes a fixed offset (VMXNET3_XDP_HEADROOM), but the XDP BPF program could have moved xdp->data. While the passed buf_size is correct (xdpf->len), the dma_addr needs to have a dynamic offset which can be calculated as xdpf->data - (void *)xdpf, that is, xdp->data - xdp->data_hard_start.

Weakness

The product writes data past the end, or before the beginning, of the intended buffer.

Affected Software

Potential Mitigations

• Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

• For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer.

• Be wary that a language’s interface to native code may still be subject to overflows, even if the language itself is theoretically safe.

• Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

• Examples include the Safe C String Library (SafeStr) by Messier and Viega [REF-57], and the Strsafe.h library from Microsoft [REF-56]. These libraries provide safer versions of overflow-prone string-handling functions.

• Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking.

• D3-SFCV (Stack Frame Canary Validation) from D3FEND [REF-1334] discusses canary-based detection in detail.

• Consider adhering to the following rules when allocating and managing an application’s memory:

• Run or compile the software using features or extensions that randomly arrange the positions of a program’s executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.

• Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as “rebasing” (for Windows) and “prelinking” (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking.

• For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].

• Use a CPU and operating system that offers Data Execution Protection (using hardware NX or XD bits) or the equivalent techniques that simulate this feature in software, such as PaX [REF-60] [REF-61]. These techniques ensure that any instruction executed is exclusively at a memory address that is part of the code segment.

• For more information on these techniques see D3-PSEP (Process Segment Execution Prevention) from D3FEND [REF-1336].

References

• https://git.kernel.org/stable/c/4678adf94da4a9e9683817b246b58ce15fb81782
• https://git.kernel.org/stable/c/59ba6cdadb9c26b606a365eb9c9b25eb2052622d
• https://git.kernel.org/stable/c/f82eb34fb59a8fb96c19f4f492c20eb774140bb5