Messages in this thread | | | Date | Wed, 2 Nov 2011 12:19:29 -0700 | From | Greg KH <> | Subject | Re: mm: avoid null pointer access in vm_struct via /proc/vmallocinfo |
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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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