Re: [PATCH bpf-next 2/4] bpf, sockmap: Fix memleak in tcp_bpf_sendmsg while sk msg is full

[wangyufen <wangyufen@huawei.com>]

在 2022/3/1 12:02, John Fastabend 写道:
> Wang Yufen wrote:
>> 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.
>
>> 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 <wangyufen@huawei.com>
>> ---
>>   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>
> .