[PATCH bpf v2 2/3] tcp: Skip cond_resched() in inet_csk_listen_stop() under BPF context

[Jiayuan Chen]

bpf_sock_destroy() runs from the tcp iterator, under rcu_read_lock(). If
the sock is a listener that still has children in its accept queue,
tcp_abort() ends up in inet_csk_listen_stop() and the cond_resched()
there trips the debug check:

BUG: sleeping function called from invalid context at net/ipv4/inet_connection_sock.c:1523
in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 628, name: test_progs
preempt_count: 0, expected: 0
RCU nest depth: 1, expected: 0
locks held by test_progs/628: 3, last CPU#3:
 #0: ffff8881158cee18 (&p->lock){+.+.}-{4:4}, at: bpf_seq_read+0x56/0x1210
 #1: ffff8881106bb858 (sk_lock-AF_INET6){+.+.}-{0:0}, at: bpf_iter_tcp_seq_show+0x32b/0x4b0
 #2: ffffffffb435af20 (rcu_read_lock){....}-{1:3}, at: bpf_iter_run_prog+0x46b/0xde0
CPU: 3 UID: 0 PID: 628 Comm: test_progs Tainted: G        W           7.2.0+ #65 PREEMPT
Tainted: [W]=WARN
Call Trace:
 <TASK>
 dump_stack_lvl+0xc1/0xf0
 dump_stack+0x10/0x20
 __might_resched+0x3d2/0x610
 inet_csk_listen_stop+0x7b/0xbf0
 tcp_abort+0x23b/0x3b0
 bpf_sock_destroy+0xfc/0x140
 bpf_prog_448133d24601754f_iter_tcp6_server+0x81/0x8a
 bpf_iter_run_prog+0x538/0xde0
 bpf_iter_tcp_seq_show+0x26b/0x4b0
 bpf_seq_read+0x424/0x1210
 vfs_read+0x197/0xe40
 ksys_read+0x119/0x240
 __x64_sys_read+0x72/0xc0
 x64_sys_call+0x647/0x27e0
 do_syscall_64+0xe5/0x610
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7fad39b28aca
RSP: 002b:00007ffc381c61c0 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007ffc381c6a88 RCX: 00007fad39b28aca
RDX: 0000000000000032 RSI: 00007ffc381c6250 RDI: 0000000000000014
RBP: 00007ffc381c61e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003
R13: 0000000000000000 R14: 000055f077c1bbb0 R15: 00007fad3a0f3000
 </TASK>

The commit that added the kfunc already guards lock_sock() in tcp_abort()
and udp_abort() with has_current_bpf_ctx(), but missed the listener path.
Do the same for the cond_resched(), it can't reschedule there anyway.

Fixes: 4ddbcb886268 ("bpf: Add bpf_sock_destroy kfunc")
Signed-off-by: Jiayuan Chen <jiayuan.chen@xxxxxxxxx>
---
 net/ipv4/inet_connection_sock.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 6257459bcee2..6a30f1138454 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -1520,7 +1520,8 @@ void inet_csk_listen_stop(struct sock *sk)
 		local_bh_enable();
 		sock_put(child);
 
-		cond_resched();
+		if (!has_current_bpf_ctx())
+			cond_resched();
 	}
 	if (queue->fastopenq.rskq_rst_head) {
 		/* Free all the reqs queued in rskq_rst_head. */
-- 
2.43.0