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SubjectRe: mm: avoid null pointer access in vm_struct via /proc/vmallocinfo
Hi Greg,

> So, if someone wants this patch there, could they please provide me with
> a backported version?

I'd like to send the patch for backport version.

Regards,


(2011/11/03 4:19), Greg KH wrote:
> Is this patch also relevant for the .32-stable tree? I tried to
> backport it, and only got one conflict, but I'm still not sure I got it
> correct.
>
> So, if someone wants this patch there, could they please provide me with
> a backported version?
>
> thanks,
>
> greg k-h
>
> On Mon, Oct 31, 2011 at 05:08:13PM -0700, Mitsuo Hayasaka wrote:
>> From: Mitsuo Hayasaka <mitsuo.hayasaka.hu@hitachi.com>
>>
>> commit f5252e009d5b87071a919221e4f6624184005368 upstream.
>>
>> 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.
>>
>> Why this happens: In __vmalloc_node_range() called from vmalloc(), newly
>> allocated vm_struct is added to vmlist at __get_vm_area_node() and then,
>> some fields of vm_struct such as nr_pages and pages are set at
>> __vmalloc_area_node(). In other words, it is added to vmlist before it is
>> fully initialized. At the same time, when the /proc/vmallocinfo is read,
>> it accesses the pages field of vm_struct according to the nr_pages field
>> at show_numa_info(). Thus, a null pointer access happens.
>>
>> The patch adds the newly allocated vm_struct to the vmlist *after* it is
>> fully initialized. So, it can avoid accessing the pages field with
>> unallocated page when show_numa_info() is called.
>>
>> Signed-off-by: Mitsuo Hayasaka <mitsuo.hayasaka.hu@hitachi.com>
>> Cc: Andrew Morton <akpm@linux-foundation.org>
>> Cc: David Rientjes <rientjes@google.com>
>> Cc: Namhyung Kim <namhyung@gmail.com>
>> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
>> Cc: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
>> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
>> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
>> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
>>
>> --- a/include/linux/vmalloc.h
>> +++ b/include/linux/vmalloc.h
>> @@ -13,6 +13,7 @@ struct vm_area_struct; /* vma defining user mapping in mm_types.h */
>> #define VM_MAP 0x00000004 /* vmap()ed pages */
>> #define VM_USERMAP 0x00000008 /* suitable for remap_vmalloc_range */
>> #define VM_VPAGES 0x00000010 /* buffer for pages was vmalloc'ed */
>> +#define VM_UNLIST 0x00000020 /* vm_struct is not listed in vmlist */
>> /* bits [20..32] reserved for arch specific ioremap internals */
>>
>> /*
>> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
>> index 5016f19..56faf31 100644
>> --- a/mm/vmalloc.c
>> +++ b/mm/vmalloc.c
>> @@ -1253,18 +1253,22 @@ EXPORT_SYMBOL_GPL(map_vm_area);
>> DEFINE_RWLOCK(vmlist_lock);
>> struct vm_struct *vmlist;
>>
>> -static void insert_vmalloc_vm(struct vm_struct *vm, struct vmap_area *va,
>> +static void setup_vmalloc_vm(struct vm_struct *vm, struct vmap_area *va,
>> unsigned long flags, void *caller)
>> {
>> - struct vm_struct *tmp, **p;
>> -
>> vm->flags = flags;
>> vm->addr = (void *)va->va_start;
>> vm->size = va->va_end - va->va_start;
>> vm->caller = caller;
>> va->private = vm;
>> va->flags |= VM_VM_AREA;
>> +}
>> +
>> +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);
>> }
>>
>> +static void insert_vmalloc_vm(struct vm_struct *vm, struct vmap_area *va,
>> + unsigned long flags, void *caller)
>> +{
>> + setup_vmalloc_vm(vm, va, flags, caller);
>> + insert_vmalloc_vmlist(vm);
>> +}
>> +
>> static struct vm_struct *__get_vm_area_node(unsigned long size,
>> unsigned long align, unsigned long flags, unsigned long start,
>> unsigned long end, int node, gfp_t gfp_mask, void *caller)
>> @@ -1313,7 +1324,18 @@ static struct vm_struct *__get_vm_area_node(unsigned long size,
>> return NULL;
>> }
>>
>> - insert_vmalloc_vm(area, va, flags, caller);
>> + /*
>> + * When this function is called from __vmalloc_node_range,
>> + * we do not add vm_struct to vmlist here to avoid
>> + * accessing uninitialized members of vm_struct such as
>> + * pages and nr_pages fields. They will be set later.
>> + * To distinguish it from others, we use a VM_UNLIST flag.
>> + */
>> + if (flags & VM_UNLIST)
>> + setup_vmalloc_vm(area, va, flags, caller);
>> + else
>> + insert_vmalloc_vm(area, va, flags, caller);
>> +
>> return area;
>> }
>>
>> @@ -1381,17 +1403,20 @@ struct vm_struct *remove_vm_area(const void *addr)
>> va = find_vmap_area((unsigned long)addr);
>> if (va && va->flags & VM_VM_AREA) {
>> struct vm_struct *vm = va->private;
>> - struct vm_struct *tmp, **p;
>> - /*
>> - * remove from list and disallow access to this vm_struct
>> - * before unmap. (address range confliction is maintained by
>> - * vmap.)
>> - */
>> - write_lock(&vmlist_lock);
>> - for (p = &vmlist; (tmp = *p) != vm; p = &tmp->next)
>> - ;
>> - *p = tmp->next;
>> - write_unlock(&vmlist_lock);
>> +
>> + if (!(vm->flags & VM_UNLIST)) {
>> + struct vm_struct *tmp, **p;
>> + /*
>> + * remove from list and disallow access to
>> + * this vm_struct before unmap. (address range
>> + * confliction is maintained by vmap.)
>> + */
>> + write_lock(&vmlist_lock);
>> + for (p = &vmlist; (tmp = *p) != vm; p = &tmp->next)
>> + ;
>> + *p = tmp->next;
>> + write_unlock(&vmlist_lock);
>> + }
>>
>> vmap_debug_free_range(va->va_start, va->va_end);
>> free_unmap_vmap_area(va);
>> @@ -1602,8 +1627,8 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
>> if (!size || (size >> PAGE_SHIFT) > totalram_pages)
>> return NULL;
>>
>> - area = __get_vm_area_node(size, align, VM_ALLOC, start, end, node,
>> - gfp_mask, caller);
>> + area = __get_vm_area_node(size, align, VM_ALLOC | VM_UNLIST,
>> + start, end, node, gfp_mask, caller);
>>
>> if (!area)
>> return NULL;
>> @@ -1611,6 +1636,12 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
>> addr = __vmalloc_area_node(area, gfp_mask, prot, node, caller);
>>
>> /*
>> + * In this function, newly allocated vm_struct is not added
>> + * to vmlist at __get_vm_area_node(). so, it is added here.
>> + */
>> + insert_vmalloc_vmlist(area);
>> +
>> + /*
>> * A ref_count = 3 is needed because the vm_struct and vmap_area
>> * structures allocated in the __get_vm_area_node() function contain
>> * references to the virtual address of the vmalloc'ed block.
>



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