[093/200] mm/vmalloc.c:__vmalloc_area_node(): avoid 32-bit overflow

Commit Message

Andrew Morton Dec. 15, 2020, 3:08 a.m. UTC

From: Andrew Morton <[e-mail]>
Subject: mm/vmalloc.c:__vmalloc_area_node(): avoid 32-bit overflow

With a machine with 3 TB (more than 2 TB memory).  If you use vmalloc to
allocate > 2 TB memory, the array_size below will be overflowed.

The array_size is an unsigned int and can only be used to allocate less
than 2 TB memory.  If you pass 2*1028*1028*1024*1024 = 2 * 2^40 in the
argument of vmalloc.  The array_size will become 2*2^31 = 2^32.  The 2^32
cannot be store with a 32 bit integer.

The fix is to change the type of array_size to unsigned long.

[[e-mail]: rework for current mainline]
Link: https://bugzilla.kernel.org/show_bug.cgi?id=210023
Reported-by: <[e-mail]>
Cc: Matthew Wilcox <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/vmalloc.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Patch

--- a/mm/vmalloc.c~mm-vmallocc-__vmalloc_area_node-avoid-32-bit-overflow
+++ a/mm/vmalloc.c
@@ -2461,9 +2461,11 @@  static void *__vmalloc_area_node(struct
 {
 	const gfp_t nested_gfp = (gfp_mask & GFP_RECLAIM_MASK) | __GFP_ZERO;
 	unsigned int nr_pages = get_vm_area_size(area) >> PAGE_SHIFT;
-	unsigned int array_size = nr_pages * sizeof(struct page *), i;
+	unsigned long array_size;
+	unsigned int i;
 	struct page **pages;
 
+	array_size = (unsigned long)nr_pages * sizeof(struct page *);
 	gfp_mask |= __GFP_NOWARN;
 	if (!(gfp_mask & (GFP_DMA | GFP_DMA32)))
 		gfp_mask |= __GFP_HIGHMEM;