On Fri, Jun 16, 2023 at 04:16:28PM +0000, Edgecombe, Rick P wrote:

On Fri, 2023-06-16 at 11:50 +0300, Mike Rapoport wrote:

quoted

-void *module_alloc(unsigned long size)
-{
-       gfp_t gfp_mask = GFP_KERNEL;
-       void *p;
-
-       if (PAGE_ALIGN(size) > MODULES_LEN)
-               return NULL;
+static struct execmem_params execmem_params = {
+       .modules = {
+               .flags = EXECMEM_KASAN_SHADOW,
+               .text = {
+                       .alignment = MODULE_ALIGN,
+               },
+       },
+};

Did you consider making these execmem_params's ro_after_init? Not that
it is security sensitive, but it's a nice hint to the reader that it is
only modified at init. And I guess basically free sanitizing of buggy
writes to it.

Makes sense.
 

quoted

 
-       p = __vmalloc_node_range(size, MODULE_ALIGN,
-                                MODULES_VADDR +
get_module_load_offset(),
-                                MODULES_END, gfp_mask, PAGE_KERNEL,
-                                VM_FLUSH_RESET_PERMS |
VM_DEFER_KMEMLEAK,
-                                NUMA_NO_NODE,
__builtin_return_address(0));
+struct execmem_params __init *execmem_arch_params(void)
+{
+       unsigned long start = MODULES_VADDR +
get_module_load_offset();

I think we can drop the mutex's in get_module_load_offset() now, since
execmem_arch_params() should only be called once at init.

Right. Even more, the entire get_module_load_offset() can be folded into
execmem_arch_params() as 

	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && kaslr_enabled())
		module_load_offset =
			get_random_u32_inclusive(1, 1024) * PAGE_SIZE;

quoted

 
-       if (p && (kasan_alloc_module_shadow(p, size, gfp_mask) < 0))
{
-               vfree(p);
-               return NULL;
-       }
+       execmem_params.modules.text.start = start;
+       execmem_params.modules.text.end = MODULES_END;
+       execmem_params.modules.text.pgprot = PAGE_KERNEL;
 
-       return p;
+       return &execmem_params;
 }
 

-- 
Sincerely yours,
Mike.