[PATCH] mm: module_alloc: check if size is 0

H. Peter Anvin
2012-03-01T20:46:57Z

On 03/01/2012 11:45 AM, Veli-Pekka Peltola wrote:
> diff --git a/arch/arm/kernel/module.c b/arch/arm/kernel/module.c
> index 1e9be5d..d44d212 100644
> --- a/arch/arm/kernel/module.c
> +++ b/arch/arm/kernel/module.c
> @@ -39,8 +39,8 @@
> #ifdef CONFIG_MMU
> void *module_alloc(unsigned long size)
> {
> - return __vmalloc_node_range(size, 1, MODULES_VADDR, MODULES_END,
> - GFP_KERNEL, PAGE_KERNEL_EXEC, -1,
> + return size == 0 ? NULL : __vmalloc_node_range(size, 1, MODULES_VADDR,
> + MODULES_END, GFP_KERNEL, PAGE_KERNEL_EXEC, -1,
> __builtin_return_address(0));
> }
> #endif
> diff --git a/arch/mips/kernel/module.c b/arch/mips/kernel/module.c
> index a5066b1..cd768e9 100644
> --- a/arch/mips/kernel/module.c
> +++ b/arch/mips/kernel/module.c
> @@ -47,8 +47,8 @@ static DEFINE_SPINLOCK(dbe_lock);
> #ifdef MODULE_START
> void *module_alloc(unsigned long size)
> {
> - return __vmalloc_node_range(size, 1, MODULE_START, MODULE_END,
> - GFP_KERNEL, PAGE_KERNEL, -1,
> + return size == 0 ? NULL : __vmalloc_node_range(size, 1, MODULE_START,
> + MODULE_END, GFP_KERNEL, PAGE_KERNEL, -1,
> __builtin_return_address(0));
> }
> #endif
> diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
> index 925179f..bff6118 100644
> --- a/arch/x86/kernel/module.c
> +++ b/arch/x86/kernel/module.c
> @@ -38,7 +38,7 @@
>
> void *module_alloc(unsigned long size)
> {
> - if (PAGE_ALIGN(size) > MODULES_LEN)
> + if (size == 0 || PAGE_ALIGN(size) > MODULES_LEN)
> return NULL;
> return __vmalloc_node_range(size, 1, MODULES_VADDR, MODULES_END,
> GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL_EXEC,

Looks good stylistically but really awkward technically.

I would like to suggest using the idiom:

if (!size)
return NULL;

... consistently; combined with the PAGE_ALIGN() clause for x86 is fine too.

-hpa

--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.