From: Jakub Sitnicki <jakub@cloudflare.com>
Date: Sun, 7 Jun 2020 22:52:28 +0200
Subject: bpf, sockhash: Fix memory leak when unlinking sockets in
 sock_hash_free
Patch-mainline: v5.8-rc1
Git-commit: 33a7c831565c43a7ee2f38c7df4c4a40e1dfdfed
References: bsc#1177028

When sockhash gets destroyed while sockets are still linked to it, we will
walk the bucket lists and delete the links. However, we are not freeing the
list elements after processing them, leaking the memory.

The leak can be triggered by close()'ing a sockhash map when it still
contains sockets, and observed with kmemleak:

  unreferenced object 0xffff888116e86f00 (size 64):
    comm "race_sock_unlin", pid 223, jiffies 4294731063 (age 217.404s)
    hex dump (first 32 bytes):
      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
      81 de e8 41 00 00 00 00 c0 69 2f 15 81 88 ff ff  ...A.....i/.....
    backtrace:
      [<00000000dd089ebb>] sock_hash_update_common+0x4ca/0x760
      [<00000000b8219bd5>] sock_hash_update_elem+0x1d2/0x200
      [<000000005e2c23de>] __do_sys_bpf+0x2046/0x2990
      [<00000000d0084618>] do_syscall_64+0xad/0x9a0
      [<000000000d96f263>] entry_SYSCALL_64_after_hwframe+0x49/0xb3

Fix it by freeing the list element when we're done with it.

Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface")
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200607205229.2389672-2-jakub@cloudflare.com
Acked-by: Gary Lin <glin@suse.com>
---
 net/core/sock_map.c |    1 +
 1 file changed, 1 insertion(+)

--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -1024,6 +1024,7 @@ static void sock_hash_free(struct bpf_ma
 			sock_map_unref(elem->sk, elem);
 			rcu_read_unlock();
 			release_sock(elem->sk);
+			sock_hash_free_elem(htab, elem);
 		}
 	}