Commit f5252e00 authored by Mitsuo Hayasaka's avatar Mitsuo Hayasaka Committed by Linus Torvalds
Browse files

mm: avoid null pointer access in vm_struct via /proc/vmallocinfo 



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: default avatarMitsuo 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>
Cc: <stable@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 8c5fb8ea

include/linux/vmalloc.h

+1 −0
Original line number Diff line number Diff line
@@ -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 */



/*

mm/vmalloc.c

+48 −17
Original line number Diff line number Diff line
@@ -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;

	}



	/*

	 * 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;



		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.)

			 * 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);
@@ -1602,14 +1627,20 @@ 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;



	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

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