From: Anastasia Kovaleva <a.kovaleva@xxxxxxxxx>
Date: Thu, 3 Oct 2024 13:44:31 +0300
> The kernel may crash when deleting a genetlink family if there are still
> listeners for that family:
>
> Oops: Kernel access of bad area, sig: 11 [#1]
> ...
> NIP [c000000000c080bc] netlink_update_socket_mc+0x3c/0xc0
> LR [c000000000c0f764] __netlink_clear_multicast_users+0x74/0xc0
> Call Trace:
> __netlink_clear_multicast_users+0x74/0xc0
> genl_unregister_family+0xd4/0x2d0
>
> Change the unsafe loop on the list to a safe one, because inside the
> loop there is an element removal from this list.
>
> Fixes: b8273570f802 ("genetlink: fix netns vs. netlink table locking (2)")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Anastasia Kovaleva <a.kovaleva@xxxxxxxxx>
> Reviewed-by: Dmitry Bogdanov <d.bogdanov@xxxxxxxxx>
Reviewed-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
> ---
> v3: remove trailing "\", change spaces to tab
> v2: add CC tag for stable
> ---
> include/net/sock.h | 2 ++
> net/netlink/af_netlink.c | 3 ++-
> 2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/include/net/sock.h b/include/net/sock.h
> index c58ca8dd561b..db29c39e19a7 100644
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
> @@ -894,6 +894,8 @@ static inline void sk_add_bind_node(struct sock *sk,
> hlist_for_each_entry_safe(__sk, tmp, list, sk_node)
> #define sk_for_each_bound(__sk, list) \
> hlist_for_each_entry(__sk, list, sk_bind_node)
> +#define sk_for_each_bound_safe(__sk, tmp, list) \
> + hlist_for_each_entry_safe(__sk, tmp, list, sk_bind_node)
>
> /**
> * sk_for_each_entry_offset_rcu - iterate over a list at a given struct offset
> diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
> index 0b7a89db3ab7..0a9287fadb47 100644
> --- a/net/netlink/af_netlink.c
> +++ b/net/netlink/af_netlink.c
> @@ -2136,8 +2136,9 @@ void __netlink_clear_multicast_users(struct sock *ksk, unsigned int group)
> {
> struct sock *sk;
> struct netlink_table *tbl = &nl_table[ksk->sk_protocol];
> + struct hlist_node *tmp;
>
> - sk_for_each_bound(sk, &tbl->mc_list)
> + sk_for_each_bound_safe(sk, tmp, &tbl->mc_list)
> netlink_update_socket_mc(nlk_sk(sk), group, 0);
> }
>
> --
> 2.40.1
