Re: [PATCH -next] netlabel: Fix memory leak in netlbl_mgmt_add_common

[Paul Moore <paul@paul-moore.com>]

On Wed, Jun 9, 2021 at 9:29 PM Liu Shixin <liushixin2@huawei.com> wrote:
>
> Hulk Robot reported memory leak in netlbl_mgmt_add_common.
> The problem is non-freed map in case of netlbl_domhsh_add() failed.
>
> BUG: memory leak
> unreferenced object 0xffff888100ab7080 (size 96):
>   comm "syz-executor537", pid 360, jiffies 4294862456 (age 22.678s)
>   hex dump (first 32 bytes):
>     05 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     fe 00 00 00 00 00 00 00 00 00 00 00 00 00 00 01  ................
>   backtrace:
>     [<0000000008b40026>] netlbl_mgmt_add_common.isra.0+0xb2a/0x1b40
>     [<000000003be10950>] netlbl_mgmt_add+0x271/0x3c0
>     [<00000000c70487ed>] genl_family_rcv_msg_doit.isra.0+0x20e/0x320
>     [<000000001f2ff614>] genl_rcv_msg+0x2bf/0x4f0
>     [<0000000089045792>] netlink_rcv_skb+0x134/0x3d0
>     [<0000000020e96fdd>] genl_rcv+0x24/0x40
>     [<0000000042810c66>] netlink_unicast+0x4a0/0x6a0
>     [<000000002e1659f0>] netlink_sendmsg+0x789/0xc70
>     [<000000006e43415f>] sock_sendmsg+0x139/0x170
>     [<00000000680a73d7>] ____sys_sendmsg+0x658/0x7d0
>     [<0000000065cbb8af>] ___sys_sendmsg+0xf8/0x170
>     [<0000000019932b6c>] __sys_sendmsg+0xd3/0x190
>     [<00000000643ac172>] do_syscall_64+0x37/0x90
>     [<000000009b79d6dc>] entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> Fixes: 63c416887437 ("netlabel: Add network address selectors to the NetLabel/LSM domain mapping")
> Reported-by: Hulk Robot <hulkci@huawei.com>
> Signed-off-by: Liu Shixin <liushixin2@huawei.com>
> ---
>  net/netlabel/netlabel_mgmt.c | 20 ++++++++++++++++----
>  1 file changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/net/netlabel/netlabel_mgmt.c b/net/netlabel/netlabel_mgmt.c
> index e664ab990941..e7f00c0f441e 100644
> --- a/net/netlabel/netlabel_mgmt.c
> +++ b/net/netlabel/netlabel_mgmt.c
> @@ -191,6 +191,12 @@ static int netlbl_mgmt_add_common(struct genl_info *info,
>                 entry->family = AF_INET;
>                 entry->def.type = NETLBL_NLTYPE_ADDRSELECT;
>                 entry->def.addrsel = addrmap;
> +
> +               ret_val = netlbl_domhsh_add(entry, audit_info);
> +               if (ret_val != 0) {
> +                       kfree(map);
> +                       goto add_free_addrmap;
> +               }
>  #if IS_ENABLED(CONFIG_IPV6)
>         } else if (info->attrs[NLBL_MGMT_A_IPV6ADDR]) {
>                 struct in6_addr *addr;
> @@ -243,13 +249,19 @@ static int netlbl_mgmt_add_common(struct genl_info *info,
>                 entry->family = AF_INET6;
>                 entry->def.type = NETLBL_NLTYPE_ADDRSELECT;
>                 entry->def.addrsel = addrmap;
> +
> +               ret_val = netlbl_domhsh_add(entry, audit_info);
> +               if (ret_val != 0) {
> +                       kfree(map);
> +                       goto add_free_addrmap;
> +               }
>  #endif /* IPv6 */
> +       } else {
> +               ret_val = netlbl_domhsh_add(entry, audit_info);
> +               if (ret_val != 0)
> +                       goto add_free_addrmap;
>         }
>
> -       ret_val = netlbl_domhsh_add(entry, audit_info);
> -       if (ret_val != 0)
> -               goto add_free_addrmap;
> -
>         return 0;

Thanks for the report and a fix, although I think there may be a
simpler fix that results in less code duplication; some quick pseudo
code below:

  int netlbl_mgmt_add_common(...)
  {
     void *map_p = NULL;

     if (NLBL_MGMT_A_IPV4ADDR) {
       struct netlbl_domaddr4_map *map;
       map_p = map;

     } else if (NLBL_MGMT_A_IPV6ADDR) {
       struct netlbl_domaddr4_map *map;
       map_p = map;
    }

  add_free_addrmap:
    kfree(map_p);
    kfree(addrmap);
  }

... this approach would even simplify the error handling after the
netlbl_af{4,6}list_add() calls a bit too (you could jump straight to
add_free_addrmap).

-- 
paul moore
www.paul-moore.com