net: fix memory leak in tcp_conn_request()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: net: fix memory leak in tcp_conn_request() If inet_csk_reqsk_queue_hash_add() return false, tcp_conn_request() will return without free the dst memory, which allocated in af_ops->route_req. Here is the kmemleak stack: unreferenced object 0xffff8881198631c0 (size 240): comm "softirq", pid 0, jiffies 4299266571 (age 1802.392s) hex dump (first 32 bytes): 00 10 9b 03 81 88 ff ff 80 98 da bc ff ff ff ff ................ 81 55 18 bb ff ff ff ff 00 00 00 00 00 00 00 00 .U.............. backtrace: [<ffffffffb93e8d4c>] kmem_cache_alloc+0x60c/0xa80 [<ffffffffba11b4c5>] dst_alloc+0x55/0x250 [<ffffffffba227bf6>] rt_dst_alloc+0x46/0x1d0 [<ffffffffba23050a>] __mkroute_output+0x29a/0xa50 [<ffffffffba23456b>] ip_route_output_key_hash+0x10b/0x240 [<ffffffffba2346bd>] ip_route_output_flow+0x1d/0x90 [<ffffffffba254855>] inet_csk_route_req+0x2c5/0x500 [<ffffffffba26b331>] tcp_conn_request+0x691/0x12c0 [<ffffffffba27bd08>] tcp_rcv_state_process+0x3c8/0x11b0 [<ffffffffba2965c6>] tcp_v4_do_rcv+0x156/0x3b0 [<ffffffffba299c98>] tcp_v4_rcv+0x1cf8/0x1d80 [<ffffffffba239656>] ip_protocol_deliver_rcu+0xf6/0x360 [<ffffffffba2399a6>] ip_local_deliver_finish+0xe6/0x1e0 [<ffffffffba239b8e>] ip_local_deliver+0xee/0x360 [<ffffffffba239ead>] ip_rcv+0xad/0x2f0 [<ffffffffba110943>] __netif_receive_skb_one_core+0x123/0x140 Call dst_release() to free the dst memory when inet_csk_reqsk_queue_hash_add() return false in tcp_conn_request().

References

• https://git.kernel.org/stable/c/9d38959677291552d1b0ed2689a540af279b5bf8
• https://git.kernel.org/stable/c/de3f999bf8aee16e9da1c1224191abdc69e97c9d
• https://git.kernel.org/stable/c/2af69905180b3fea12f9c1db374b153a06977021
• https://git.kernel.org/stable/c/b0b190218c78d8aeecfba36ea3a90063b3ede52d
• https://git.kernel.org/stable/c/4f4aa4aa28142d53f8b06585c478476cfe325cfc