Re: [PATCH] audit: fix memory leak in nf_tables_commit

[Dongliang Mu]

On Tue, Jul 13, 2021 at 7:47 PM Lukas Bulwahn <lukas.bulwahn@xxxxxxxxx> wrote:
>
> On Tue, Jul 13, 2021 at 11:42 AM Dongliang Mu <mudongliangabcd@xxxxxxxxx> 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@xxxxxxxxxxxxxxxx>
>
> 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
>

Hi Lukas,

this bug is not listed on the syzbot dashboard. I found this bug by
setting up a local syzkaller instance, so I only list syzbot other
than concrete syzbot id.

best regards,
Dongliang Mu

> as in for example:
>
> Reported-by: syzbot+fee64147a25aecd48055@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> A rough count says that format above is used 1300 times, whereas
>
> Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
>
> is only used about 330 times.
>
>
> Lukas
>
> > Fixes: c520292f29b8 ("audit: log nftables configuration change events once per table")
> > Signed-off-by: Dongliang Mu <mudongliangabcd@xxxxxxxxx>
> > ---
> >  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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