From: Anastasia Kovaleva a.kovaleva@yadro.com 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@vger.kernel.org Signed-off-by: Anastasia Kovaleva a.kovaleva@yadro.com Reviewed-by: Dmitry Bogdanov d.bogdanov@yadro.com

Reviewed-by: Kuniyuki Iwashima kuniyu@amazon.com

---

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