netdev - [PATCH net-next] net: bpf: Use sockopt_lock_sock() in ip_sock_set

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Date: Fri, 27 Oct 2023 11:24:24 -0700
From: Yonghong Song <yonghong.song@...ux.dev>
To: bpf@...r.kernel.org,
	netdev@...r.kernel.org
Cc: Alexei Starovoitov <ast@...nel.org>,
	Andrii Nakryiko <andrii@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	kernel-team@...com,
	Eric Dumazet <edumazet@...gle.com>,
	Martin KaFai Lau <martin.lau@...nel.org>
Subject: [PATCH net-next] net: bpf: Use sockopt_lock_sock() in ip_sock_set_tos()

With latest sync from net-next tree, bpf-next has a bpf selftest failure:
  [root@...h-fb-vm1 bpf]# ./test_progs -t setget_sockopt
  ...
  [   76.194349] ============================================
  [   76.194682] WARNING: possible recursive locking detected
  [   76.195039] 6.6.0-rc7-g37884503df08-dirty #67 Tainted: G        W  OE
  [   76.195518] --------------------------------------------
  [   76.195852] new_name/154 is trying to acquire lock:
  [   76.196159] ffff8c3e06ad8d30 (sk_lock-AF_INET){+.+.}-{0:0}, at: ip_sock_set_tos+0x19/0x30
  [   76.196669]
  [   76.196669] but task is already holding lock:
  [   76.197028] ffff8c3e06ad8d30 (sk_lock-AF_INET){+.+.}-{0:0}, at: inet_listen+0x21/0x70
  [   76.197517]
  [   76.197517] other info that might help us debug this:
  [   76.197919]  Possible unsafe locking scenario:
  [   76.197919]
  [   76.198287]        CPU0
  [   76.198444]        ----
  [   76.198600]   lock(sk_lock-AF_INET);
  [   76.198831]   lock(sk_lock-AF_INET);
  [   76.199062]
  [   76.199062]  *** DEADLOCK ***
  [   76.199062]
  [   76.199420]  May be due to missing lock nesting notation
  [   76.199420]
  [   76.199879] 2 locks held by new_name/154:
  [   76.200131]  #0: ffff8c3e06ad8d30 (sk_lock-AF_INET){+.+.}-{0:0}, at: inet_listen+0x21/0x70
  [   76.200644]  #1: ffffffff90f96a40 (rcu_read_lock){....}-{1:2}, at: __cgroup_bpf_run_filter_sock_ops+0x55/0x290
  [   76.201268]
  [   76.201268] stack backtrace:
  [   76.201538] CPU: 4 PID: 154 Comm: new_name Tainted: G        W  OE      6.6.0-rc7-g37884503df08-dirty #67
  [   76.202134] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
  [   76.202699] Call Trace:
  [   76.202858]  <TASK>
  [   76.203002]  dump_stack_lvl+0x4b/0x80
  [   76.203239]  __lock_acquire+0x740/0x1ec0
  [   76.203503]  lock_acquire+0xc1/0x2a0
  [   76.203766]  ? ip_sock_set_tos+0x19/0x30
  [   76.204050]  ? sk_stream_write_space+0x12a/0x230
  [   76.204389]  ? lock_release+0xbe/0x260
  [   76.204661]  lock_sock_nested+0x32/0x80
  [   76.204942]  ? ip_sock_set_tos+0x19/0x30
  [   76.205208]  ip_sock_set_tos+0x19/0x30
  [   76.205452]  do_ip_setsockopt+0x4b3/0x1580
  [   76.205719]  __bpf_setsockopt+0x62/0xa0
  [   76.205963]  bpf_sock_ops_setsockopt+0x11/0x20
  [   76.206247]  bpf_prog_630217292049c96e_bpf_test_sockopt_int+0xbc/0x123
  [   76.206660]  bpf_prog_493685a3bae00bbd_bpf_test_ip_sockopt+0x49/0x4b
  [   76.207055]  bpf_prog_b0bcd27f269aeea0_skops_sockopt+0x44c/0xec7
  [   76.207437]  __cgroup_bpf_run_filter_sock_ops+0xda/0x290
  [   76.207829]  __inet_listen_sk+0x108/0x1b0
  [   76.208122]  inet_listen+0x48/0x70
  [   76.208373]  __sys_listen+0x74/0xb0
  [   76.208630]  __x64_sys_listen+0x16/0x20
  [   76.208911]  do_syscall_64+0x3f/0x90
  [   76.209174]  entry_SYSCALL_64_after_hwframe+0x6e/0xd8
  ...

Both ip_sock_set_tos() and inet_listen() calls lock_sock(sk) which
caused a dead lock.

To fix the issue, use sockopt_lock_sock() in ip_sock_set_tos()
instead. sockopt_lock_sock() will avoid lock_sock() if it is in bpf
context.

Fixes: 878d951c6712 ("inet: lock the socket in ip_sock_set_tos()")
Cc: Eric Dumazet <edumazet@...gle.com>
Suggested-by: Martin KaFai Lau <martin.lau@...nel.org>
Signed-off-by: Yonghong Song <yonghong.song@...ux.dev>
---
 net/ipv4/ip_sockglue.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index 9c68b6b74d9f..2efc53526a38 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -602,9 +602,9 @@ void __ip_sock_set_tos(struct sock *sk, int val)
 
 void ip_sock_set_tos(struct sock *sk, int val)
 {
-	lock_sock(sk);
+	sockopt_lock_sock(sk);
 	__ip_sock_set_tos(sk, val);
-	release_sock(sk);
+	sockopt_release_sock(sk);
 }
 EXPORT_SYMBOL(ip_sock_set_tos);
 
-- 
2.34.1