linux-kernel - Re: [syzbot] [bpf?] [net?] possible deadlock in scheduler

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Date: Thu, 21 Mar 2024 07:51:26 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+628f63ef3b071e16463e@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [bpf?] [net?] possible deadlock in scheduler_tick (3)

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git  ea80e3ed09ab

--- x/net/core/sock_map.c
+++ y/net/core/sock_map.c
@@ -932,11 +932,12 @@ static long sock_hash_delete_elem(struct
 	struct bpf_shtab_bucket *bucket;
 	struct bpf_shtab_elem *elem;
 	int ret = -ENOENT;
+	unsigned long flags;
 
 	hash = sock_hash_bucket_hash(key, key_size);
 	bucket = sock_hash_select_bucket(htab, hash);
 
-	spin_lock_bh(&bucket->lock);
+	spin_lock_irqsave(&bucket->lock, flags);
 	elem = sock_hash_lookup_elem_raw(&bucket->head, hash, key, key_size);
 	if (elem) {
 		hlist_del_rcu(&elem->node);
@@ -944,7 +945,7 @@ static long sock_hash_delete_elem(struct
 		sock_hash_free_elem(htab, elem);
 		ret = 0;
 	}
-	spin_unlock_bh(&bucket->lock);
+	spin_unlock_irqrestore(&bucket->lock, flags);
 	return ret;
 }
 
@@ -1143,6 +1144,8 @@ static void sock_hash_free(struct bpf_ma
 	 */
 	synchronize_rcu();
 	for (i = 0; i < htab->buckets_num; i++) {
+		unsigned long flags;
+
 		bucket = sock_hash_select_bucket(htab, i);
 
 		/* We are racing with sock_hash_delete_from_link to
@@ -1151,11 +1154,11 @@ static void sock_hash_free(struct bpf_ma
 		 * exists, psock exists and holds a ref to socket. That
 		 * lets us to grab a socket ref too.
 		 */
-		spin_lock_bh(&bucket->lock);
+		spin_lock_irqsave(&bucket->lock, flags);
 		hlist_for_each_entry(elem, &bucket->head, node)
 			sock_hold(elem->sk);
 		hlist_move_list(&bucket->head, &unlink_list);
-		spin_unlock_bh(&bucket->lock);
+		spin_unlock_irqrestore(&bucket->lock, flags);
 
 		/* Process removed entries out of atomic context to
 		 * block for socket lock before deleting the psock's
--