mm/vmalloc.c: don't dereference possible NULL pointer in __vunmap()

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@dudau.co.uk
Fixes: f3c01d2f3ade ("mm: vmalloc: avoid racy handling of debugobjects in vunmap")
Signed-off-by: Liviu Dudau <liviu@dudau.co.uk>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Chintan Pandya <cpandya@codeaurora.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 871e41c55e239afb83051d8e73fde088d746ba37..806047d7fda3c3fd6b06126f1c59358b3a0ee66c 100644 (file)
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1505,7 +1505,7 @@ static void __vunmap(const void *addr, int deallocate_pages)
                        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);