[PATCH] mm/vmalloc: Sanitize __get_vm_area() arguments

Peter Zijlstra
2020-04-03T16:33:08Z

__get_vm_area() is an exported symbol, make sure the callers stay in
the expected memory range. When calling this function with memory
ranges outside of the VMALLOC range *bad* things can happen.

(I noticed this when I managed to corrupt the kernel text by accident)

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
mm/vmalloc.c | 7 +++++++
1 file changed, 7 insertions(+)

--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2130,6 +2130,13 @@ static struct vm_struct *__get_vm_area_n
struct vm_struct *__get_vm_area(unsigned long size, unsigned long flags,
unsigned long start, unsigned long end)
{
+ /*
+ * Ensure callers stay in the vmalloc range.
+ */
+ if (WARN_ON(start < VMALLOC_START || start > VMALLOC_END ||
+ end < VMALLOC_START || end > VMALLOC_END))
+ return NULL;
+
return __get_vm_area_node(size, 1, flags, start, end, NUMA_NO_NODE,
GFP_KERNEL, __builtin_return_address(0));
}