net: Fix an unsafe loop on the list

commit 1dae9f1187189bc09ff6d25ca97ead711f7e26f9 upstream.

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>
Link: https://patch.msgid.link/20241003104431.12391-1-a.kovaleva@yadro.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/net/sock.h b/include/net/sock.h
index 146f1b9c3063652c11a2d75520f029ea428809fe..1680d6dc4d19e6e4c435fee0cfbefb79b4011b94 100644 (file)
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -850,6 +850,8 @@ 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 258d885548ae470ece6b389c3b7f00e7e33331b7..fdcb10abebfd1ed6e3e5525166e15ee6fced8fa2 100644 (file)
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2159,8 +2159,9 @@ 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);
 }