[PATCH 4.9 59/61] mm/vmalloc.c: dont dereference possible NULL pointer in __vunmap()

[Greg Kroah-Hartman]

From: Liviu Dudau <li...@dudau.co.uk>

commit 6ade20327dbb808882888ed8ccded71e93067cf9 upstream.

find_vmap_area() can return a NULL pointer and we're going to
dereference it without checking it first.  Use the existing
find_vm_area() function which does exactly what we want and checks for
the NULL pointer.

Link: http://lkml.kernel.org/r/20181228171009.22269-1-li...@dudau.co.uk
Fixes: f3c01d2f3ade ("mm: vmalloc: avoid racy handling of debugobjects in 
vunmap")
Signed-off-by: Liviu Dudau <li...@dudau.co.uk>
Reviewed-by: Andrew Morton <a...@linux-foundation.org>
Cc: Chintan Pandya <cpan...@codeaurora.org>
Cc: Andrey Ryabinin <aryabi...@virtuozzo.com>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Cc: Guenter Roeck <li...@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 mm/vmalloc.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1499,7 +1499,7 @@ static void __vunmap(const void *addr, i
                        addr))
                return;
 
-       area = find_vmap_area((unsigned long)addr)->vm;
+       area = find_vm_area(addr);
        if (unlikely(!area)) {
                WARN(1, KERN_ERR "Trying to vfree() nonexistent vm area (%p)\n",
                                addr);