From: Florian Westphal fw@strlen.de
[ Upstream commit e6d57e9ff0aec323717ee36fc9ea34ad89217151 ]
nf_conntrack_hash_check_insert() callers free the ct entry directly, via nf_conntrack_free.
This isn't safe anymore because nf_conntrack_hash_check_insert() might place the entry into the conntrack table and then delteted the entry again because it found that a conntrack extension has been removed at the same time.
In this case, the just-added entry is removed again and an error is returned to the caller.
Problem is that another cpu might have picked up this entry and incremented its reference count.
This results in a use-after-free/double-free, once by the other cpu and once by the caller of nf_conntrack_hash_check_insert().
Fix this by making nf_conntrack_hash_check_insert() not fail anymore after the insertion, just like before the 'Fixes' commit.
This is safe because a racing nf_ct_iterate() has to wait for us to release the conntrack hash spinlocks.
While at it, make the function return -EAGAIN in the rmmod (genid changed) case, this makes nfnetlink replay the command (suggested by Pablo Neira).
Fixes: c56716c69ce1 ("netfilter: extensions: introduce extension genid count") Signed-off-by: Florian Westphal fw@strlen.de Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/netfilter/nf_conntrack_bpf.c | 1 - net/netfilter/nf_conntrack_core.c | 25 +++++++++++++++---------- net/netfilter/nf_conntrack_netlink.c | 3 --- 3 files changed, 15 insertions(+), 14 deletions(-)
diff --git a/net/netfilter/nf_conntrack_bpf.c b/net/netfilter/nf_conntrack_bpf.c index 24002bc61e07e..e1af14e3b63c5 100644 --- a/net/netfilter/nf_conntrack_bpf.c +++ b/net/netfilter/nf_conntrack_bpf.c @@ -381,7 +381,6 @@ struct nf_conn *bpf_ct_insert_entry(struct nf_conn___init *nfct_i) struct nf_conn *nfct = (struct nf_conn *)nfct_i; int err;
- nfct->status |= IPS_CONFIRMED; err = nf_conntrack_hash_check_insert(nfct); if (err < 0) { nf_conntrack_free(nfct); diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c index 496c4920505b3..ead11a9c261f3 100644 --- a/net/netfilter/nf_conntrack_core.c +++ b/net/netfilter/nf_conntrack_core.c @@ -886,10 +886,8 @@ nf_conntrack_hash_check_insert(struct nf_conn *ct)
zone = nf_ct_zone(ct);
- if (!nf_ct_ext_valid_pre(ct->ext)) { - NF_CT_STAT_INC_ATOMIC(net, insert_failed); - return -ETIMEDOUT; - } + if (!nf_ct_ext_valid_pre(ct->ext)) + return -EAGAIN;
local_bh_disable(); do { @@ -924,6 +922,19 @@ nf_conntrack_hash_check_insert(struct nf_conn *ct) goto chaintoolong; }
+ /* If genid has changed, we can't insert anymore because ct + * extensions could have stale pointers and nf_ct_iterate_destroy + * might have completed its table scan already. + * + * Increment of the ext genid right after this check is fine: + * nf_ct_iterate_destroy blocks until locks are released. + */ + if (!nf_ct_ext_valid_post(ct->ext)) { + err = -EAGAIN; + goto out; + } + + ct->status |= IPS_CONFIRMED; smp_wmb(); /* The caller holds a reference to this object */ refcount_set(&ct->ct_general.use, 2); @@ -932,12 +943,6 @@ nf_conntrack_hash_check_insert(struct nf_conn *ct) NF_CT_STAT_INC(net, insert); local_bh_enable();
- if (!nf_ct_ext_valid_post(ct->ext)) { - nf_ct_kill(ct); - NF_CT_STAT_INC_ATOMIC(net, drop); - return -ETIMEDOUT; - } - return 0; chaintoolong: NF_CT_STAT_INC(net, chaintoolong); diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c index ca4d5bb1ea524..733bb56950c14 100644 --- a/net/netfilter/nf_conntrack_netlink.c +++ b/net/netfilter/nf_conntrack_netlink.c @@ -2316,9 +2316,6 @@ ctnetlink_create_conntrack(struct net *net, nfct_seqadj_ext_add(ct); nfct_synproxy_ext_add(ct);
- /* we must add conntrack extensions before confirmation. */ - ct->status |= IPS_CONFIRMED; - if (cda[CTA_STATUS]) { err = ctnetlink_change_status(ct, cda); if (err < 0)