Re: [syzbot] [bpf?] [net?] possible deadlock in tick_setup_sched_timer

From: Edward Adam Davis
Date: Sat Mar 30 2024 - 06:28:51 EST


please test dl in tick_setup_sched_timer

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git fe46a7dd189e

diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index 27d733c0f65e..ae8f81b26e16 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -932,11 +932,12 @@ static long sock_hash_delete_elem(struct bpf_map *map, void *key)
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 bpf_map *map, void *key)
sock_hash_free_elem(htab, elem);
ret = 0;
}
- spin_unlock_bh(&bucket->lock);
+ spin_unlock_irqrestore(&bucket->lock, flags);
return ret;
}

@@ -1136,6 +1137,7 @@ static void sock_hash_free(struct bpf_map *map)
struct bpf_shtab_elem *elem;
struct hlist_node *node;
int i;
+ unsigned long flags;

/* After the sync no updates or deletes will be in-flight so it
* is safe to walk map and remove entries without risking a race
@@ -1151,11 +1153,11 @@ static void sock_hash_free(struct bpf_map *map)
* 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