On Tue, Sep 06, 2016 at 09:57:23AM +0800, fgao@xxxxxxxxxx wrote:
> From: Gao Feng <fgao@xxxxxxxxxx>
>
> When memory is exhausted, nfct_seqadj_ext_add may fail to add the seqadj
> extension. But the function nf_ct_seqadj_init doesn't check if get valid
> seqadj pointer by the nfct_seqadj.
>
> Now drop the packet directly when fail to add seqadj extension to avoid
> dereference NULL pointer in nf_ct_seqadj_init.
>
> Signed-off-by: Gao Feng <fgao@xxxxxxxxxx>
> ---
> v4: Drop the packet directly when fail to add seqadj extension;
> v3: Remove the warning log when seqadj is null;
> v2: Remove the unnessary seqadj check in nf_ct_seq_adjust
> v1: Initial patch
>
> net/netfilter/nf_conntrack_core.c | 6 +++++-
> net/netfilter/nf_nat_core.c | 3 ++-
> 2 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
> index dd2c43a..dfa76ce 100644
> --- a/net/netfilter/nf_conntrack_core.c
> +++ b/net/netfilter/nf_conntrack_core.c
> @@ -1036,7 +1036,11 @@ init_conntrack(struct net *net, struct nf_conn *tmpl,
> return (struct nf_conntrack_tuple_hash *)ct;
>
> if (tmpl && nfct_synproxy(tmpl)) {
> - nfct_seqadj_ext_add(ct);
> + if (!nfct_seqadj_ext_add(ct)) {
> + nf_conntrack_free(ct);
> + pr_debug("Can't add seqadj extension\n");
> + return NULL;
> + }
> nfct_synproxy_ext_add(ct);
I think this is part of the same logical change, ie. nf_ct_ext_add()
returns NULL, then I would also fix nfct_synproxy_ext_add() in this
go.
> }
>
> diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c
> index de31818..b82282a 100644
> --- a/net/netfilter/nf_nat_core.c
> +++ b/net/netfilter/nf_nat_core.c
> @@ -441,7 +441,8 @@ nf_nat_setup_info(struct nf_conn *ct,
> ct->status |= IPS_DST_NAT;
>
> if (nfct_help(ct))
> - nfct_seqadj_ext_add(ct);
> + if (!nfct_seqadj_ext_add(ct))
> + return NF_DROP;
ctnetlink may have created a conntrack with seqadj in place by when we
call nf_nat_setup_info() so NF_ACCEPT would be more conservative, eg.
via conntrackd state synchronization.
Actually, after a quick look at ctnetlink, I don't see any any call to
nfct_seqadj_ext_add() from there, so I suspect this is broken since
SYNPROXY was introduced. It would be great if you can review this and
send us patches to fix this, if indeed needed.
Thanks!
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