On Fri 11-03-22 17:36:24, Miaohe Lin wrote:
> If mpol_new is allocated but not used in restart loop, mpol_new will be
> freed via mpol_put before returning to the caller. But refcnt is not
> initialized yet, so mpol_put could not do the right things and might
> leak the unused mpol_new.
The code is really hideous but is there really any bug there? AFAICS the
new policy is only allocated in if (n->end > end) branch and that one
will set the reference count on the retry. Or am I missing something?
> Fixes: 42288fe366c4 ("mm: mempolicy: Convert shared_policy mutex to spinlock")
> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> ---
> mm/mempolicy.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 34d2b29c96ad..f19f19d3558b 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -2733,6 +2733,7 @@ static int shared_policy_replace(struct shared_policy *sp, unsigned long start,
> mpol_new = kmem_cache_alloc(policy_cache, GFP_KERNEL);
> if (!mpol_new)
> goto err_out;
> + refcount_set(&mpol_new->refcnt, 1);
> goto restart;
> }
>
> --
> 2.23.0
--
Michal Hocko
SUSE Labs
