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

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Date: Tue, 21 May 2024 18:35:21 +0200
From: Jakub Sitnicki <jakub@...udflare.com>
To: syzbot <syzbot+ec941d6e24f633a59172@...kaller.appspotmail.com>
Cc: andrii@...nel.org,  ast@...nel.org,  bpf@...r.kernel.org,
  daniel@...earbox.net,  davem@...emloft.net,  edumazet@...gle.com,
  john.fastabend@...il.com,  kuba@...nel.org,
  linux-kernel@...r.kernel.org,  netdev@...r.kernel.org,
  pabeni@...hat.com,  syzkaller-bugs@...glegroups.com,
  xrivendell7@...il.com
Subject: Re: [syzbot] [net?] [bpf?] possible deadlock in
 sock_hash_delete_elem (2)

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git main

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 77da1f438bec..f6e694457886 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -8882,7 +8882,8 @@ static bool may_update_sockmap(struct bpf_verifier_env *env, int func_id)
 	enum bpf_attach_type eatype = env->prog->expected_attach_type;
 	enum bpf_prog_type type = resolve_prog_type(env->prog);
 
-	if (func_id != BPF_FUNC_map_update_elem)
+	if (func_id != BPF_FUNC_map_update_elem &&
+	    func_id != BPF_FUNC_map_delete_elem)
 		return false;
 
 	/* It's not possible to get access to a locked struct sock in these
@@ -8988,7 +8989,6 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
 	case BPF_MAP_TYPE_SOCKMAP:
 		if (func_id != BPF_FUNC_sk_redirect_map &&
 		    func_id != BPF_FUNC_sock_map_update &&
-		    func_id != BPF_FUNC_map_delete_elem &&
 		    func_id != BPF_FUNC_msg_redirect_map &&
 		    func_id != BPF_FUNC_sk_select_reuseport &&
 		    func_id != BPF_FUNC_map_lookup_elem &&
@@ -8998,7 +8998,6 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
 	case BPF_MAP_TYPE_SOCKHASH:
 		if (func_id != BPF_FUNC_sk_redirect_hash &&
 		    func_id != BPF_FUNC_sock_hash_update &&
-		    func_id != BPF_FUNC_map_delete_elem &&
 		    func_id != BPF_FUNC_msg_redirect_hash &&
 		    func_id != BPF_FUNC_sk_select_reuseport &&
 		    func_id != BPF_FUNC_map_lookup_elem &&