[PATCH 3.10 64/74] mm/vmalloc.c: fix an overflow bug in alloc_vmap_area()

[Greg Kroah-Hartman]

3.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Zhang Yanfei <zhangyanfei.yes@xxxxxxxxx>

commit bcb615a81b1765864c71c50afb56631e7a1e5283 upstream.

When searching a vmap area in the vmalloc space, we use (addr + size -
1) to check if the value is less than addr, which is an overflow.  But
we assign (addr + size) to vmap_area->va_end.

So if we come across the below case:

  (addr + size - 1) : not overflow
  (addr + size)     : overflow

we will assign an overflow value (e.g 0) to vmap_area->va_end, And this
will trigger BUG in __insert_vmap_area, causing system panic.

So using (addr + size) to check the overflow should be the correct
behaviour, not (addr + size - 1).

Signed-off-by: Zhang Yanfei <zhangyanfei@xxxxxxxxxxxxxx>
Reported-by: Ghennadi Procopciuc <unix140@xxxxxxxxx>
Tested-by: Daniel Baluta <dbaluta@xxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Anatoly Muliarski <x86ever@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 mm/vmalloc.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -388,12 +388,12 @@ nocache:
 		addr = ALIGN(first->va_end, align);
 		if (addr < vstart)
 			goto nocache;
-		if (addr + size - 1 < addr)
+		if (addr + size < addr)
 			goto overflow;
 
 	} else {
 		addr = ALIGN(vstart, align);
-		if (addr + size - 1 < addr)
+		if (addr + size < addr)
 			goto overflow;
 
 		n = vmap_area_root.rb_node;
@@ -420,7 +420,7 @@ nocache:
 		if (addr + cached_hole_size < first->va_start)
 			cached_hole_size = first->va_start - addr;
 		addr = ALIGN(first->va_end, align);
-		if (addr + size - 1 < addr)
+		if (addr + size < addr)
 			goto overflow;
 
 		if (list_is_last(&first->list, &vmap_area_list))


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