netdev - Re: [PATCH] audit: fix memory leak in nf_tables

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Message-ID: <CAKXUXMwMvWmS1jMfGe15tJKXpKdqGnhjsOhBKPkQ6_+twZpKxA@mail.gmail.com>
Date:   Tue, 13 Jul 2021 13:47:14 +0200
From:   Lukas Bulwahn <lukas.bulwahn@...il.com>
To:     Dongliang Mu <mudongliangabcd@...il.com>
Cc:     Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paul Moore <paul@...l-moore.com>,
        Richard Guy Briggs <rgb@...hat.com>,
        syzbot <syzkaller@...glegroups.com>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        Netdev <netdev@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] audit: fix memory leak in nf_tables_commit

On Tue, Jul 13, 2021 at 11:42 AM Dongliang Mu <mudongliangabcd@...il.com> wrote:
>
> In nf_tables_commit, if nf_tables_commit_audit_alloc fails, it does not
> free the adp variable.
>
> Fix this by freeing the linked list with head adl.
>
> backtrace:
>   kmalloc include/linux/slab.h:591 [inline]
>   kzalloc include/linux/slab.h:721 [inline]
>   nf_tables_commit_audit_alloc net/netfilter/nf_tables_api.c:8439 [inline]
>   nf_tables_commit+0x16e/0x1760 net/netfilter/nf_tables_api.c:8508
>   nfnetlink_rcv_batch+0x512/0xa80 net/netfilter/nfnetlink.c:562
>   nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:634 [inline]
>   nfnetlink_rcv+0x1fa/0x220 net/netfilter/nfnetlink.c:652
>   netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
>   netlink_unicast+0x2c7/0x3e0 net/netlink/af_netlink.c:1340
>   netlink_sendmsg+0x36b/0x6b0 net/netlink/af_netlink.c:1929
>   sock_sendmsg_nosec net/socket.c:702 [inline]
>   sock_sendmsg+0x56/0x80 net/socket.c:722
>
> Reported-by: syzbot <syzkaller@...glegroups.com>

As far as I see, the more default way is to reference to syzbot by:

Reported-by: syzbot+[[20-letter hex reference]]@syzkaller.appspotmail.com

as in for example:

Reported-by: syzbot+fee64147a25aecd48055@...kaller.appspotmail.com

A rough count says that format above is used 1300 times, whereas

Reported-by: syzbot <syzkaller@...glegroups.com>

is only used about 330 times.


Lukas

> Fixes: c520292f29b8 ("audit: log nftables configuration change events once per table")
> Signed-off-by: Dongliang Mu <mudongliangabcd@...il.com>
> ---
>  net/netfilter/nf_tables_api.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
> index 390d4466567f..7f45b291be13 100644
> --- a/net/netfilter/nf_tables_api.c
> +++ b/net/netfilter/nf_tables_api.c
> @@ -8444,6 +8444,16 @@ static int nf_tables_commit_audit_alloc(struct list_head *adl,
>         return 0;
>  }
>
> +static void nf_tables_commit_free(struct list_head *adl)
> +{
> +       struct nft_audit_data *adp, *adn;
> +
> +       list_for_each_entry_safe(adp, adn, adl, list) {
> +               list_del(&adp->list);
> +               kfree(adp);
> +       }
> +}
> +
>  static void nf_tables_commit_audit_collect(struct list_head *adl,
>                                            struct nft_table *table, u32 op)
>  {
> @@ -8508,6 +8518,7 @@ static int nf_tables_commit(struct net *net, struct sk_buff *skb)
>                 ret = nf_tables_commit_audit_alloc(&adl, trans->ctx.table);
>                 if (ret) {
>                         nf_tables_commit_chain_prepare_cancel(net);
> +                       nf_tables_commit_free(adl);
>                         return ret;
>                 }
>                 if (trans->msg_type == NFT_MSG_NEWRULE ||
> @@ -8517,6 +8528,7 @@ static int nf_tables_commit(struct net *net, struct sk_buff *skb)
>                         ret = nf_tables_commit_chain_prepare(net, chain);
>                         if (ret < 0) {
>                                 nf_tables_commit_chain_prepare_cancel(net);
> +                               nf_tables_commit_free(adl);
>                                 return ret;
>                         }
>                 }
> --
> 2.25.1
>
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