Re: [PATCH net] ipv6: addrlabel: fix possible memory leak in ip6addrlbl_net_init

[wanghai (M)]

在 2020/11/24 9:22, Jakub Kicinski 写道:
On Sun, 22 Nov 2020 10:34:56 +0800 Wang Hai wrote:
kmemleak report a memory leak as follows:

unreferenced object 0xffff8880059c6a00 (size 64):
   comm "ip", pid 23696, jiffies 4296590183 (age 1755.384s)
   hex dump (first 32 bytes):
     20 01 00 10 00 00 00 00 00 00 00 00 00 00 00 00   ...............
     1c 00 00 00 00 00 00 00 00 00 00 00 07 00 00 00  ................
   backtrace:
     [<00000000aa4e7a87>] ip6addrlbl_add+0x90/0xbb0
     [<0000000070b8d7f1>] ip6addrlbl_net_init+0x109/0x170
     [<000000006a9ca9d4>] ops_init+0xa8/0x3c0
     [<000000002da57bf2>] setup_net+0x2de/0x7e0
     [<000000004e52d573>] copy_net_ns+0x27d/0x530
     [<00000000b07ae2b4>] create_new_namespaces+0x382/0xa30
     [<000000003b76d36f>] unshare_nsproxy_namespaces+0xa1/0x1d0
     [<0000000030653721>] ksys_unshare+0x3a4/0x780
     [<0000000007e82e40>] __x64_sys_unshare+0x2d/0x40
     [<0000000031a10c08>] do_syscall_64+0x33/0x40
     [<0000000099df30e7>] entry_SYSCALL_64_after_hwframe+0x44/0xa9

We should free all rules when we catch an error in ip6addrlbl_net_init().
otherwise a memory leak will occur.

Fixes: 2a8cc6c89039 ("[IPV6] ADDRCONF: Support RFC3484 configurable address 
selection policy table.")
Reported-by: Hulk Robot <hul...@huawei.com>
Signed-off-by: Wang Hai <wangha...@huawei.com>
We can simplify this function.

diff --git a/net/ipv6/addrlabel.c b/net/ipv6/addrlabel.c
index 642fc6ac13d2..637e323a0224 100644
--- a/net/ipv6/addrlabel.c
+++ b/net/ipv6/addrlabel.c
@@ -306,6 +306,8 @@ static int ip6addrlbl_del(struct net *net,
  /* add default label */
  static int __net_init ip6addrlbl_net_init(struct net *net)
  {
+       struct ip6addrlbl_entry *p = NULL;
+       struct hlist_node *n;
        int err = 0;
err does not need init

        int i;
  
@@ -320,9 +322,17 @@ static int __net_init ip6addrlbl_net_init(struct net *net)
instead of the temporary ret variable we can assign directly to err

                                         ip6addrlbl_init_table[i].prefixlen,
                                         0,
                                         ip6addrlbl_init_table[i].label, 0);
-               /* XXX: should we free all rules when we catch an error? */
-               if (ret && (!err || err != -ENOMEM))
+               if (ret && (!err || err != -ENOMEM)) {
this will become if (err)

                        err = ret;
+                       goto err_ip6addrlbl_add;
+               }
+       }
+       return err;
return 0;

+err_ip6addrlbl_add:
+       hlist_for_each_entry_safe(p, n, &net->ipv6.ip6addrlbl_table.head, list) 
{
+               hlist_del_rcu(&p->list);
+               kfree_rcu(p, rcu);
        }
        return err;
  }

Thanks for advice. I just sent a v2

“[PATCH net v2] ipv6: addrlabel: fix possible memory leak in 
ip6addrlbl_net_init”

.