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authorFlorian Westphal <fw@strlen.de>2021-09-13 14:42:33 +0200
committerPablo Neira Ayuso <pablo@netfilter.org>2021-09-21 03:46:55 +0200
commita499b03bf36b0c2e3b958a381d828678ab0ffc5e (patch)
tree8cafe425042022c6be918922292743f9b42cacd1 /net
parentcb89f63ba662d2b56583f4dd3dd2b7f03b6d6587 (diff)
netfilter: nf_tables: unlink table before deleting it
syzbot reports following UAF: BUG: KASAN: use-after-free in memcmp+0x18f/0x1c0 lib/string.c:955 nla_strcmp+0xf2/0x130 lib/nlattr.c:836 nft_table_lookup.part.0+0x1a2/0x460 net/netfilter/nf_tables_api.c:570 nft_table_lookup net/netfilter/nf_tables_api.c:4064 [inline] nf_tables_getset+0x1b3/0x860 net/netfilter/nf_tables_api.c:4064 nfnetlink_rcv_msg+0x659/0x13f0 net/netfilter/nfnetlink.c:285 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2504 Problem is that all get operations are lockless, so the commit_mutex held by nft_rcv_nl_event() isn't enough to stop a parallel GET request from doing read-accesses to the table object even after synchronize_rcu(). To avoid this, unlink the table first and store the table objects in on-stack scratch space. Fixes: 6001a930ce03 ("netfilter: nftables: introduce table ownership") Reported-and-tested-by: syzbot+f31660cf279b0557160c@syzkaller.appspotmail.com Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Diffstat (limited to 'net')
-rw-r--r--net/netfilter/nf_tables_api.c28
1 files changed, 18 insertions, 10 deletions
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 081437dd75b7..33e771cd847c 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -9599,7 +9599,6 @@ static void __nft_release_table(struct net *net, struct nft_table *table)
table->use--;
nf_tables_chain_destroy(&ctx);
}
- list_del(&table->list);
nf_tables_table_destroy(&ctx);
}
@@ -9612,6 +9611,8 @@ static void __nft_release_tables(struct net *net)
if (nft_table_has_owner(table))
continue;
+ list_del(&table->list);
+
__nft_release_table(net, table);
}
}
@@ -9619,31 +9620,38 @@ static void __nft_release_tables(struct net *net)
static int nft_rcv_nl_event(struct notifier_block *this, unsigned long event,
void *ptr)
{
+ struct nft_table *table, *to_delete[8];
struct nftables_pernet *nft_net;
struct netlink_notify *n = ptr;
- struct nft_table *table, *nt;
struct net *net = n->net;
- bool release = false;
+ unsigned int deleted;
+ bool restart = false;
if (event != NETLINK_URELEASE || n->protocol != NETLINK_NETFILTER)
return NOTIFY_DONE;
nft_net = nft_pernet(net);
+ deleted = 0;
mutex_lock(&nft_net->commit_mutex);
+again:
list_for_each_entry(table, &nft_net->tables, list) {
if (nft_table_has_owner(table) &&
n->portid == table->nlpid) {
__nft_release_hook(net, table);
- release = true;
+ list_del_rcu(&table->list);
+ to_delete[deleted++] = table;
+ if (deleted >= ARRAY_SIZE(to_delete))
+ break;
}
}
- if (release) {
+ if (deleted) {
+ restart = deleted >= ARRAY_SIZE(to_delete);
synchronize_rcu();
- list_for_each_entry_safe(table, nt, &nft_net->tables, list) {
- if (nft_table_has_owner(table) &&
- n->portid == table->nlpid)
- __nft_release_table(net, table);
- }
+ while (deleted)
+ __nft_release_table(net, to_delete[--deleted]);
+
+ if (restart)
+ goto again;
}
mutex_unlock(&nft_net->commit_mutex);