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" alway 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: 1f5be6b3b063 ("udp: Implement udp_bpf_recvmsg() for sockmap")
Fixes: 9825d866ce0d ("af_unix: Implement unix_dgram_bpf_recvmsg()")
Fixes: c5d2177a72a1 ("bpf, sockmap: Fix race in ingress receive verdict with redirect to self")
Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface")
Signed-off-by: Liu Jian <liujian56@xxxxxxxxxx>
---
net/ipv4/tcp_bpf.c | 6 ++++++
net/ipv4/udp_bpf.c | 3 +++
net/unix/unix_bpf.c | 3 +++
3 files changed, 12 insertions(+)
diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
index cf26d65ca389..36b52ae519ab 100644
--- a/net/ipv4/tcp_bpf.c
+++ b/net/ipv4/tcp_bpf.c
@@ -186,6 +186,9 @@ static int tcp_bpf_recvmsg_parser(struct sock *sk,
if (unlikely(flags & MSG_ERRQUEUE))
return inet_recv_error(sk, msg, len, addr_len);
+ if (len == 0)
+ return 0;
+
psock = sk_psock_get(sk);
if (unlikely(!psock))
return tcp_recvmsg(sk, msg, len, flags, addr_len);
@@ -244,6 +247,9 @@ static int tcp_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
if (unlikely(flags & MSG_ERRQUEUE))
return inet_recv_error(sk, msg, len, addr_len);
+ if (len == 0)
+ return 0;
+
psock = sk_psock_get(sk);
if (unlikely(!psock))
return tcp_recvmsg(sk, msg, len, flags, addr_len);
diff --git a/net/ipv4/udp_bpf.c b/net/ipv4/udp_bpf.c
index e5dc91d0e079..a2a9d67bd3ff 100644
--- a/net/ipv4/udp_bpf.c
+++ b/net/ipv4/udp_bpf.c
@@ -68,6 +68,9 @@ static int udp_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
if (unlikely(flags & MSG_ERRQUEUE))
return inet_recv_error(sk, msg, len, addr_len);
+ if (len == 0)
+ return 0;
+
psock = sk_psock_get(sk);
if (unlikely(!psock))
return sk_udp_recvmsg(sk, msg, len, flags, addr_len);
diff --git a/net/unix/unix_bpf.c b/net/unix/unix_bpf.c
index e9bf15513961..851c4719f8a9 100644
--- a/net/unix/unix_bpf.c
+++ b/net/unix/unix_bpf.c
@@ -54,6 +54,9 @@ static int unix_bpf_recvmsg(struct sock *sk, struct msghdr *msg,
struct sk_psock *psock;
int copied;
+ if (len == 0)
+ return 0;
+
psock = sk_psock_get(sk);
if (unlikely(!psock))
return __unix_recvmsg(sk, msg, len, flags);
--
2.34.1
