在 2022/3/1 12:02, John Fastabend 写道:

Wang Yufen wrote:

quoted

If tcp_bpf_sendmsg() is running while sk msg is full, sk_msg_alloc()
returns -ENOSPC, tcp_bpf_sendmsg() goto wait for memory. If partial memory
has been alloced by sk_msg_alloc(), that is, msg_tx->sg.size is greater
than osize after sk_msg_alloc(), memleak occurs. To fix we use
sk_msg_trim() to release the allocated memory, then goto wait for memory.

Small nit, "sk_msg_alloc() returns -ENOSPC" should be something like, "when
sk_msg_alloc() returns -ENOMEM error,..." That error path is from ENOMEM not
the ENOSPC.

Thanks, I will fix in v2.

But nice find thanks! I think we might have seen this in a couple cases on
our side as well.

quoted

This issue can cause the following info:
WARNING: CPU: 3 PID: 7950 at net/core/stream.c:208 sk_stream_kill_queues+0xd4/0x1a0
Call Trace:
  <TASK>
  inet_csk_destroy_sock+0x55/0x110
  __tcp_close+0x279/0x470
  tcp_close+0x1f/0x60
  inet_release+0x3f/0x80
  __sock_release+0x3d/0xb0
  sock_close+0x11/0x20
  __fput+0x92/0x250
  task_work_run+0x6a/0xa0
  do_exit+0x33b/0xb60
  do_group_exit+0x2f/0xa0
  get_signal+0xb6/0x950
  arch_do_signal_or_restart+0xac/0x2a0
  exit_to_user_mode_prepare+0xa9/0x200
  syscall_exit_to_user_mode+0x12/0x30
  do_syscall_64+0x46/0x80
  entry_SYSCALL_64_after_hwframe+0x44/0xae
  </TASK>

WARNING: CPU: 3 PID: 2094 at net/ipv4/af_inet.c:155 inet_sock_destruct+0x13c/0x260
Call Trace:
  <TASK>
  __sk_destruct+0x24/0x1f0
  sk_psock_destroy+0x19b/0x1c0
  process_one_work+0x1b3/0x3c0
  kthread+0xe6/0x110
  ret_from_fork+0x22/0x30
  </TASK>

Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface")
Signed-off-by: Wang Yufen <redacted>
---
  net/ipv4/tcp_bpf.c | 4 +++-
  1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
index 9b9b02052fd3..ac9f491cc139 100644
--- a/net/ipv4/tcp_bpf.c
+++ b/net/ipv4/tcp_bpf.c

@@ -421,8 +421,10 @@ static int tcp_bpf_sendmsg(struct sock *sk, struct msghdr *msg, size_t size)
  		osize = msg_tx->sg.size;
  		err = sk_msg_alloc(sk, msg_tx, msg_tx->sg.size + copy, msg_tx->sg.end - 1);
  		if (err) {
-			if (err != -ENOSPC)
+			if (err != -ENOSPC) {
+				sk_msg_trim(sk, msg_tx, osize);
  				goto wait_for_memory;
+			}
  			enospc = true;
  			copy = msg_tx->sg.size - osize;
  		}

-- 
2.25.1

Acked-by: John Fastabend <john.fastabend@gmail.com>
.