Re: [BUG]: mm/vmalloc: uninitialized variable access in pcpu_get_vm_areas

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On 2019-06-17 14:14, Arnd Bergmann wrote:
gcc points out some obviously broken code in linux-next

mm/vmalloc.c: In function 'pcpu_get_vm_areas':
mm/vmalloc.c:991:4: error: 'lva' may be used uninitialized in this
function [-Werror=maybe-uninitialized]
    insert_vmap_area_augment(lva, &va->rb_node,
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     &free_vmap_area_root, &free_vmap_area_list);
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mm/vmalloc.c:916:20: note: 'lva' was declared here
  struct vmap_area *lva;
                    ^~~

Remove the obviously broken code. This is almost certainly
not the correct solution, but it's what I have applied locally
to get a clean build again.

Please fix this properly.

Fixes: 68ad4a330433 ("mm/vmalloc.c: keep track of free blocks for vmap
allocation")
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
 mm/vmalloc.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index a9213fc3802d..bfcf0124a773 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -984,14 +984,9 @@ adjust_va_to_fit_type(struct vmap_area *va,
 		return -1;
 	}

-	if (type != FL_FIT_TYPE) {
+	if (type == FL_FIT_TYPE)
 		augment_tree_propagate_from(va);

-		if (type == NE_FIT_TYPE)
-			insert_vmap_area_augment(lva, &va->rb_node,
-				&free_vmap_area_root, &free_vmap_area_list);
-	}
-
 	return 0;
 }


Hi Arnd,

Seems the proper fix is just setting lva to NULL.  The only place
where lva is allocated and then used is when type == NE_FIT_TYPE,
so according to my shallow understanding of the code everything
should be fine.

--
Roman






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