bpf, sockmap: Fix memleak in tcp_bpf_sendmsg while sk msg is full

Summary

In the Linux kernel, the following vulnerability has been resolved: bpf, sockmap: Fix memleak in tcp_bpf_sendmsg while sk msg is full If tcp_bpf_sendmsg() is running while sk msg is full. When sk_msg_alloc() returns -ENOMEM error, tcp_bpf_sendmsg() goes to 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. Other call paths of sk_msg_alloc() have the similar issue, such as tls_sw_sendmsg(), so handle sk_msg_trim logic inside sk_msg_alloc(), as Cong Wang suggested. 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>