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![Liu Jian](/assets/img/avatar_default.png)
When the buffer length of the recvmsg system call is 0, we got the flollowing soft lockup problem: watchdog: BUG: soft lockup - CPU#3 stuck for 27s! [a.out:6149] CPU: 3 PID: 6149 Comm: a.out Kdump: loaded Not tainted 6.2.0+ #30 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014 RIP: 0010:remove_wait_queue+0xb/0xc0 Code: 5e 41 5f c3 cc cc cc cc 0f 1f 80 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 0f 1f 44 00 00 41 57 <41> 56 41 55 41 54 55 48 89 fd 53 48 89 f3 4c 8d 6b 18 4c 8d 73 20 RSP: 0018:ffff88811b5978b8 EFLAGS: 00000246 RAX: 0000000000000000 RBX: ffff88811a7d3780 RCX: ffffffffb7a4d768 RDX: dffffc0000000000 RSI: ffff88811b597908 RDI: ffff888115408040 RBP: 1ffff110236b2f1b R08: 0000000000000000 R09: ffff88811a7d37e7 R10: ffffed10234fa6fc R11: 0000000000000001 R12: ffff88811179b800 R13: 0000000000000001 R14: ffff88811a7d38a8 R15: ffff88811a7d37e0 FS: 00007f6fb5398740(0000) GS:ffff888237180000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020000000 CR3: 000000010b6ba002 CR4: 0000000000370ee0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> tcp_msg_wait_data+0x279/0x2f0 tcp_bpf_recvmsg_parser+0x3c6/0x490 inet_recvmsg+0x280/0x290 sock_recvmsg+0xfc/0x120 ____sys_recvmsg+0x160/0x3d0 ___sys_recvmsg+0xf0/0x180 __sys_recvmsg+0xea/0x1a0 do_syscall_64+0x3f/0x90 entry_SYSCALL_64_after_hwframe+0x72/0xdc The logic in tcp_bpf_recvmsg_parser is as follows: msg_bytes_ready: copied = sk_msg_recvmsg(sk, psock, msg, len, flags); if (!copied) { wait data; goto msg_bytes_ready; } In this case, "copied" always is 0, the infinite loop occurs. According to the Linux system call man page, 0 should be returned in this case. Therefore, in tcp_bpf_recvmsg_parser(), if the length is 0, directly return. Also modify several other functions with the same problem. Fixes:1f5be6b3b0
("udp: Implement udp_bpf_recvmsg() for sockmap") Fixes:9825d866ce
("af_unix: Implement unix_dgram_bpf_recvmsg()") Fixes:c5d2177a72
("bpf, sockmap: Fix race in ingress receive verdict with redirect to self") Fixes:604326b41a
("bpf, sockmap: convert to generic sk_msg interface") Signed-off-by: Liu Jian <liujian56@huawei.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: John Fastabend <john.fastabend@gmail.com> Cc: Jakub Sitnicki <jakub@cloudflare.com> Link: https://lore.kernel.org/bpf/20230303080946.1146638-1-liujian56@huawei.com
178 lines
4.6 KiB
C
178 lines
4.6 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/* Copyright (c) 2021 Cong Wang <cong.wang@bytedance.com> */
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#include <linux/skmsg.h>
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#include <linux/bpf.h>
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#include <net/sock.h>
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#include <net/af_unix.h>
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#define unix_sk_has_data(__sk, __psock) \
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({ !skb_queue_empty(&__sk->sk_receive_queue) || \
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!skb_queue_empty(&__psock->ingress_skb) || \
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!list_empty(&__psock->ingress_msg); \
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})
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static int unix_msg_wait_data(struct sock *sk, struct sk_psock *psock,
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long timeo)
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{
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DEFINE_WAIT_FUNC(wait, woken_wake_function);
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struct unix_sock *u = unix_sk(sk);
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int ret = 0;
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if (sk->sk_shutdown & RCV_SHUTDOWN)
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return 1;
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if (!timeo)
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return ret;
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add_wait_queue(sk_sleep(sk), &wait);
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sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk);
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if (!unix_sk_has_data(sk, psock)) {
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mutex_unlock(&u->iolock);
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wait_woken(&wait, TASK_INTERRUPTIBLE, timeo);
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mutex_lock(&u->iolock);
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ret = unix_sk_has_data(sk, psock);
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}
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sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk);
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remove_wait_queue(sk_sleep(sk), &wait);
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return ret;
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}
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static int __unix_recvmsg(struct sock *sk, struct msghdr *msg,
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size_t len, int flags)
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{
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if (sk->sk_type == SOCK_DGRAM)
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return __unix_dgram_recvmsg(sk, msg, len, flags);
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else
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return __unix_stream_recvmsg(sk, msg, len, flags);
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}
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static int unix_bpf_recvmsg(struct sock *sk, struct msghdr *msg,
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size_t len, int flags, int *addr_len)
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{
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struct unix_sock *u = unix_sk(sk);
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struct sk_psock *psock;
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int copied;
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if (!len)
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return 0;
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psock = sk_psock_get(sk);
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if (unlikely(!psock))
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return __unix_recvmsg(sk, msg, len, flags);
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mutex_lock(&u->iolock);
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if (!skb_queue_empty(&sk->sk_receive_queue) &&
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sk_psock_queue_empty(psock)) {
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mutex_unlock(&u->iolock);
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sk_psock_put(sk, psock);
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return __unix_recvmsg(sk, msg, len, flags);
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}
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msg_bytes_ready:
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copied = sk_msg_recvmsg(sk, psock, msg, len, flags);
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if (!copied) {
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long timeo;
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int data;
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timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
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data = unix_msg_wait_data(sk, psock, timeo);
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if (data) {
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if (!sk_psock_queue_empty(psock))
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goto msg_bytes_ready;
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mutex_unlock(&u->iolock);
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sk_psock_put(sk, psock);
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return __unix_recvmsg(sk, msg, len, flags);
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}
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copied = -EAGAIN;
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}
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mutex_unlock(&u->iolock);
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sk_psock_put(sk, psock);
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return copied;
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}
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static struct proto *unix_dgram_prot_saved __read_mostly;
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static DEFINE_SPINLOCK(unix_dgram_prot_lock);
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static struct proto unix_dgram_bpf_prot;
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static struct proto *unix_stream_prot_saved __read_mostly;
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static DEFINE_SPINLOCK(unix_stream_prot_lock);
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static struct proto unix_stream_bpf_prot;
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static void unix_dgram_bpf_rebuild_protos(struct proto *prot, const struct proto *base)
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{
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*prot = *base;
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prot->close = sock_map_close;
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prot->recvmsg = unix_bpf_recvmsg;
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prot->sock_is_readable = sk_msg_is_readable;
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}
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static void unix_stream_bpf_rebuild_protos(struct proto *prot,
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const struct proto *base)
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{
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*prot = *base;
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prot->close = sock_map_close;
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prot->recvmsg = unix_bpf_recvmsg;
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prot->sock_is_readable = sk_msg_is_readable;
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prot->unhash = sock_map_unhash;
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}
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static void unix_dgram_bpf_check_needs_rebuild(struct proto *ops)
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{
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if (unlikely(ops != smp_load_acquire(&unix_dgram_prot_saved))) {
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spin_lock_bh(&unix_dgram_prot_lock);
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if (likely(ops != unix_dgram_prot_saved)) {
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unix_dgram_bpf_rebuild_protos(&unix_dgram_bpf_prot, ops);
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smp_store_release(&unix_dgram_prot_saved, ops);
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}
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spin_unlock_bh(&unix_dgram_prot_lock);
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}
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}
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static void unix_stream_bpf_check_needs_rebuild(struct proto *ops)
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{
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if (unlikely(ops != smp_load_acquire(&unix_stream_prot_saved))) {
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spin_lock_bh(&unix_stream_prot_lock);
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if (likely(ops != unix_stream_prot_saved)) {
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unix_stream_bpf_rebuild_protos(&unix_stream_bpf_prot, ops);
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smp_store_release(&unix_stream_prot_saved, ops);
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}
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spin_unlock_bh(&unix_stream_prot_lock);
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}
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}
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int unix_dgram_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore)
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{
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if (sk->sk_type != SOCK_DGRAM)
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return -EOPNOTSUPP;
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if (restore) {
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sk->sk_write_space = psock->saved_write_space;
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sock_replace_proto(sk, psock->sk_proto);
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return 0;
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}
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unix_dgram_bpf_check_needs_rebuild(psock->sk_proto);
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sock_replace_proto(sk, &unix_dgram_bpf_prot);
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return 0;
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}
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int unix_stream_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore)
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{
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if (restore) {
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sk->sk_write_space = psock->saved_write_space;
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sock_replace_proto(sk, psock->sk_proto);
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return 0;
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}
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unix_stream_bpf_check_needs_rebuild(psock->sk_proto);
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sock_replace_proto(sk, &unix_stream_bpf_prot);
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return 0;
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}
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void __init unix_bpf_build_proto(void)
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{
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unix_dgram_bpf_rebuild_protos(&unix_dgram_bpf_prot, &unix_dgram_proto);
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unix_stream_bpf_rebuild_protos(&unix_stream_bpf_prot, &unix_stream_proto);
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}
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