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

From: Roman Penyaev
Date: Mon Jun 17 2019 - 09:54:50 EST

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
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)

- 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.