On Mon, Sep 13, 2021 at 02:42:33PM +0200, Florian Westphal wrote: > 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. Applied, thanks.
