lkml.org 
[lkml]   [2011]   [Nov]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: mm: avoid null pointer access in vm_struct via /proc/vmallocinfo
    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.


    \
     
     \ /
      Last update: 2011-11-02 20:23    [W:0.035 / U:29.636 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site