CVE-2024-53193

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

clk: clk-loongson2: Fix memory corruption bug in struct loongson2_clk_provider

Some heap space is allocated for the flexible structure struct clk_hw_onecell_data and its flexible-array member hws through the composite structure struct loongson2_clk_provider in function loongson2_clk_probe(), as shown below:

289 struct loongson2_clk_provider *clp; … 296 for (p = data; p->name; p++) 297 clks_num++; 298 299 clp = devm_kzalloc(dev, struct_size(clp, clk_data.hws, clks_num), 300 GFP_KERNEL);

Then some data is written into the flexible array:

350 clp->clk_data.hws[p->id] = hw;

This corrupts clk_lock, which is the spinlock variable immediately following the clk_data member in struct loongson2_clk_provider:

struct loongson2_clk_provider { void __iomem *base; struct device dev; struct clk_hw_onecell_data clk_data; spinlock_t clk_lock; / protect access to DIV registers */ };

The problem is that the flexible structure is currently placed in the middle of struct loongson2_clk_provider instead of at the end.

Fix this by moving struct clk_hw_onecell_data clk_data; to the end of struct loongson2_clk_provider. Also, add a code comment to help prevent this from happening again in case new members are added to the structure in the future.

This change also fixes the following -Wflex-array-member-not-at-end warning:

drivers/clk/clk-loongson2.c:32:36: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]

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/145de18065b9840687d9b4e63746238c1da25d22
• https://git.kernel.org/stable/c/6e4bf018bb040955da53dae9f8628ef8fcec2dbe
• https://git.kernel.org/stable/c/76918202615f2ba7deda14901d9fff528a180099