CVE-2024-53193: clk: clk-loongson2: Fix memory corruption bug in struct loongson2_clk_provider

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

clk: clk-loongson2: Fix memory corruption bug in struct loongson2clkprovider

Some heap space is allocated for the flexible structure struct clkhwonecelldata and its flexible-array member hws through the composite structure struct loongson2clkprovider in function loongson2clkprobe(), as shown below:

289 struct loongson2clkprovider clp; ... 296 for (p = data; p->name; p++) 297 clksnum++; 298 299 clp = devmkzalloc(dev, structsize(clp, clkdata.hws, clksnum), 300 GFPKERNEL);

Then some data is written into the flexible array:

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

This corrupts clklock, which is the spinlock variable immediately following the clkdata member in struct loongson2clkprovider:

struct loongson2clkprovider { void iomem base; struct device dev; struct clkhwonecelldata clkdata; spinlockt clklock; / protect access to DIV registers / };

The problem is that the flexible structure is currently placed in the middle of struct loongson2clkprovider instead of at the end.

Fix this by moving struct clkhwonecelldata clkdata; to the end of struct loongson2clkprovider. 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]