[PATCH] mm/vmalloc: unbreak kasan vmalloc support

[Daniel Axtens]

In commit 121e6f3258fe ("mm/vmalloc: hugepage vmalloc mappings"),
__vmalloc_node_range was changed such that __get_vm_area_node was no
longer called with the requested/real size of the vmalloc allocation, but
rather with a rounded-up size.

This means that __get_vm_area_node called kasan_unpoision_vmalloc() with
a rounded up size rather than the real size. This led to it allowing
access to too much memory and so missing vmalloc OOBs and failing the
kasan kunit tests.

Pass the real size and the desired shift into __get_vm_area_node. This
allows it to round up the size for the underlying allocators while
still unpoisioning the correct quantity of shadow memory.

Adjust the other call-sites to pass in PAGE_SHIFT for the shift value.

Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: David Gow <davidgow@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Cc: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=213335
Fixes: 121e6f3258fe ("mm/vmalloc: hugepage vmalloc mappings")
Signed-off-by: Daniel Axtens <dja@xxxxxxxxxx>
---
 mm/vmalloc.c | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index aaad569e8963..3471cbeb083c 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2362,15 +2362,16 @@ static void clear_vm_uninitialized_flag(struct vm_struct *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, const void *caller)
+		unsigned long align, unsigned long shift, unsigned long flags,
+		unsigned long start, unsigned long end, int node,
+		gfp_t gfp_mask, const void *caller)
 {
 	struct vmap_area *va;
 	struct vm_struct *area;
 	unsigned long requested_size = size;
 
 	BUG_ON(in_interrupt());
-	size = PAGE_ALIGN(size);
+	size = ALIGN(size, 1ul << shift);
 	if (unlikely(!size))
 		return NULL;
 
@@ -2402,8 +2403,8 @@ struct vm_struct *__get_vm_area_caller(unsigned long size, unsigned long flags,
 				       unsigned long start, unsigned long end,
 				       const void *caller)
 {
-	return __get_vm_area_node(size, 1, flags, start, end, NUMA_NO_NODE,
-				  GFP_KERNEL, caller);
+	return __get_vm_area_node(size, 1, PAGE_SHIFT, flags, start, end,
+				  NUMA_NO_NODE, GFP_KERNEL, caller);
 }
 
 /**
@@ -2419,7 +2420,8 @@ struct vm_struct *__get_vm_area_caller(unsigned long size, unsigned long flags,
  */
 struct vm_struct *get_vm_area(unsigned long size, unsigned long flags)
 {
-	return __get_vm_area_node(size, 1, flags, VMALLOC_START, VMALLOC_END,
+	return __get_vm_area_node(size, 1, PAGE_SHIFT, flags,
+				  VMALLOC_START, VMALLOC_END,
 				  NUMA_NO_NODE, GFP_KERNEL,
 				  __builtin_return_address(0));
 }
@@ -2427,7 +2429,8 @@ struct vm_struct *get_vm_area(unsigned long size, unsigned long flags)
 struct vm_struct *get_vm_area_caller(unsigned long size, unsigned long flags,
 				const void *caller)
 {
-	return __get_vm_area_node(size, 1, flags, VMALLOC_START, VMALLOC_END,
+	return __get_vm_area_node(size, 1, PAGE_SHIFT, flags,
+				  VMALLOC_START, VMALLOC_END,
 				  NUMA_NO_NODE, GFP_KERNEL, caller);
 }
 
@@ -2949,9 +2952,9 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
 	}
 
 again:
-	size = PAGE_ALIGN(size);
-	area = __get_vm_area_node(size, align, VM_ALLOC | VM_UNINITIALIZED |
-				vm_flags, start, end, node, gfp_mask, caller);
+	area = __get_vm_area_node(real_size, align, shift, VM_ALLOC |
+				  VM_UNINITIALIZED | vm_flags, start, end, node,
+				  gfp_mask, caller);
 	if (!area) {
 		warn_alloc(gfp_mask, NULL,
 			"vmalloc error: size %lu, vm_struct allocation failed",
@@ -2970,6 +2973,7 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
 	 */
 	clear_vm_uninitialized_flag(area);
 
+	size = PAGE_ALIGN(size);
 	kmemleak_vmalloc(area, size, gfp_mask);
 
 	return addr;
-- 
2.30.2