[PATCH 5.15 674/691] net: Fix an unsafe loop on the list

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5.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Anastasia Kovaleva <a.kovaleva@xxxxxxxxx>

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@xxxxxxxxxxxxxxx
Signed-off-by: Anastasia Kovaleva <a.kovaleva@xxxxxxxxx>
Reviewed-by: Dmitry Bogdanov <d.bogdanov@xxxxxxxxx>
Reviewed-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Link: https://patch.msgid.link/20241003104431.12391-1-a.kovaleva@xxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 include/net/sock.h       |    2 ++
 net/netlink/af_netlink.c |    3 ++-
 2 files changed, 4 insertions(+), 1 deletion(-)

--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -850,6 +850,8 @@ static inline void sk_add_bind_node(stru
 	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
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2159,8 +2159,9 @@ void __netlink_clear_multicast_users(str
 {
 	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);
 }
 






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