On Fri, Jul 10, 2020 at 09:40:42PM +0200, Uladzislau Rezki (Sony) wrote:
> Before triggering a BUG() it would be useful to understand
> how two areas overlap between each other. Print information
> about start/end addresses of both VAs and their addresses.
>
> For example if both are identical it could mean double free.
>
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
> ---
> mm/vmalloc.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 5a2b55c8dd9a..1679b01febcd 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -549,8 +549,13 @@ find_va_links(struct vmap_area *va,
> else if (va->va_end > tmp_va->va_start &&
> va->va_start >= tmp_va->va_end)
> link = &(*link)->rb_right;
> - else
> + else {
> + pr_err("Overlaps: 0x%px(0x%lx-0x%lx), 0x%px(0x%lx-0x%lx)\n",
> + va, va->va_start, va->va_end, tmp_va,
> + tmp_va->va_start, tmp_va->va_end);
It might be helpful to have a "vmalloc:" prefix to that string to indicate
where to start searching. And I don't think we're supposed to use %px
without a really good justification these days.
Can we do without the BUG()? Maybe just break out and decline to insert
the conflicting range?
> BUG();
> + }
> } while (*link);
>
> *parent = &tmp_va->rb_node;
> @@ -1993,6 +1998,9 @@ static void vmap_init_free_space(void)
> insert_vmap_area_augment(free, NULL,
> &free_vmap_area_root,
> &free_vmap_area_list);
> + insert_vmap_area_augment(free, NULL,
> + &free_vmap_area_root,
> + &free_vmap_area_list);
This is surely testing code that you forgot to delete?
