Re: bpf: kernel BUG in htab_elem_free

From: Daniel Borkmann
Date: Thu Nov 03 2016 - 12:39:21 EST

On 11/03/2016 03:15 PM, Dmitry Vyukov wrote:
On Wed, Nov 2, 2016 at 11:14 PM, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote:
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!

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) {
- htab_elem_free(htab, l);
+ if (l->state != HTAB_EXTRA_ELEM_USED)
+ htab_elem_free(htab, l);