[PATCH 4.4 45/48] mm/vmalloc.c: dont dereference possible NULL pointer in __vunmap()

From: Greg Kroah-Hartman
Date: Mon Jun 01 2020 - 13:57:12 EST

From: Liviu Dudau <liviu@xxxxxxxxxxx>

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-liviu@xxxxxxxxxxx
Fixes: f3c01d2f3ade ("mm: vmalloc: avoid racy handling of debugobjects in vunmap")
Signed-off-by: Liviu Dudau <liviu@xxxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Chintan Pandya <cpandya@xxxxxxxxxxxxxx>
Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1464,7 +1464,7 @@ static void __vunmap(const void *addr, i

- 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",