Re: [PATCH -v3] avoid null pointer access in vm_struct

[Wanlong Gao <wanlong.gao@gmail.com>]

Mitsuo Hayasaka <mitsuo.hayasaka.hu <at> hitachi.com> writes:

> 
> The /proc/vmallocinfo shows information about vmalloc allocations in vmlist
> that is a linklist of vm_struct. It, however, may access pages field of
> vm_struct where a page was not allocated. This results in a null pointer
> access and leads to a kernel panic.

> +static void insert_vmalloc_vmlist(struct vm_struct *vm)
> +{
> +	struct vm_struct *tmp, **p;
> 
> +	vm->flags &= ~VM_UNLIST;
>  	write_lock(&vmlist_lock);
>  	for (p = &vmlist; (tmp = *p) != NULL; p = &tmp->next) {
>  		if (tmp->addr >= vm->addr)
> @@ -1275,6 +1279,13 @@ static void insert_vmalloc_vm(struct vm_struct *vm,
struct vmap_area *va,
>  	write_unlock(&vmlist_lock);
>  }

Hi Mitsuo:
Is it needed to set the VM_UNLIST after vm_struct added to vmlist here?
or put it into lock protection?
Thanks
-Wanlong Gao


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