CVE-2024-53193: Out-of-bounds Write

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]