Re: bpf: kernel BUG in htab_elem_free

On 11/03/2016 03:15 PM, Dmitry Vyukov wrote:

On Wed, Nov 2, 2016 at 11:14 PM, Dmitry Vyukov [off-list ref] wrote:

quoted

Here we go.

The following program triggers kernel BUG in htab_elem_free.
On commit 0c183d92b20b5c84ca655b45ef57b3318b83eb9e (Oct 31).
Run as "while true; do ./a.out; done".

This one fixes it for me. Could you check it from your side as well?
I'll submit an official fix then.

Thanks a lot for the catch!
Daniel

diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 570eeca..ad1bc67 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c

@@ -687,7 +687,8 @@ static void delete_all_elements(struct bpf_htab *htab)

  		hlist_for_each_entry_safe(l, n, head, hash_node) {
  			hlist_del_rcu(&l->hash_node);
-			htab_elem_free(htab, l);
+			if (l->state != HTAB_EXTRA_ELEM_USED)
+				htab_elem_free(htab, l);
  		}
  	}
  }