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Commit a499b03b authored by Florian Westphal's avatar Florian Westphal Committed by Pablo Neira Ayuso
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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: 6001a930 ("netfilter: nftables: introduce table ownership")
Reported-and-tested-by: default avatar <syzbot+f31660cf279b0557160c@syzkaller.appspotmail.com>
Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent cb89f63b
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