netfilter: nf_tables: ensure audit reset access to table under rcu re…

…ad side lock

The table list iteration holds rcu read lock side, but recent audit code
dereferences table object out of the rcu read lock side:

[ 4137.407349] BUG: unable to handle page fault for address: 00000000001f3c50
[ 4137.407357] #PF: supervisor read access in kernel mode
[ 4137.407359] #PF: error_code(0x0000) - not-present page
[ 4137.407360] PGD 0 P4D 0
[ 4137.407363] Oops: 0000 [#1] PREEMPT SMP PTI
[ 4137.407365] CPU: 4 PID: 500177 Comm: nft Not tainted 6.5.0+ torvalds#277
[ 4137.407369] RIP: 0010:string+0x49/0xd0
[ 4137.407374] Code: ff 77 36 45 89 d1 31 f6 49 01 f9 66 45 85 d2 75 19 eb 1e 49 39 f8 76 02 88 07 48 83 c7 01 83 c6 01 48 83 c2 01 4c 39 cf 74 07 <0f> b6 02 84 c0 75 e2 4c 89 c2 e9 58 e5 ff ff 48 c7 c0 0e b2 ff 81
[ 4137.407377] RSP: 0018:ffff8881179737f0 EFLAGS: 00010286
[ 4137.407379] RAX: 00000000001f2c50 RBX: ffff888117973848 RCX: ffff0a00ffffff04
[ 4137.407380] RDX: 00000000001f3c50 RSI: 0000000000000000 RDI: 0000000000000000
[ 4137.407381] RBP: 0000000000000000 R08: 0000000000000000 R09: 00000000ffffffff
[ 4137.407383] R10: ffffffffffffffff R11: ffff88813584d200 R12: 0000000000000000
[ 4137.407384] R13: ffffffffa15cf709 R14: 0000000000000000 R15: ffffffffa15cf709
[ 4137.407385] FS:  00007fcfc18bb580(0000) GS:ffff88840e700000(0000) knlGS:0000000000000000
[ 4137.407387] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 4137.407388] CR2: 00000000001f3c50 CR3: 00000001055b2001 CR4: 00000000001706e0
[ 4137.407390] Call Trace:
[ 4137.407392]  <TASK>
[ 4137.407393]  ? __die+0x1b/0x60
[ 4137.407397]  ? page_fault_oops+0x6b/0xa0
[ 4137.407399]  ? exc_page_fault+0x60/0x120
[ 4137.407403]  ? asm_exc_page_fault+0x22/0x30
[ 4137.407408]  ? string+0x49/0xd0
[ 4137.407410]  vsnprintf+0x257/0x4f0
[ 4137.407414]  kvasprintf+0x3e/0xb0
[ 4137.407417]  kasprintf+0x3e/0x50
[ 4137.407419]  nf_tables_dump_rules+0x1c0/0x360 [nf_tables]
[ 4137.407439]  ? __alloc_skb+0xc3/0x170
[ 4137.407442]  netlink_dump+0x170/0x330
[ 4137.407447]  __netlink_dump_start+0x227/0x300
[ 4137.407449]  nf_tables_getrule+0x205/0x390 [nf_tables]

Fixes: ea078ae ("netfilter: nf_tables: Audit log rule reset")
Fixes: 7e9be11 ("netfilter: nf_tables: Audit log setelem reset")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -3538,11 +3538,12 @@ static int nf_tables_dump_rules(struct sk_buff *skb,
 			break;
 	}
 done:
-	rcu_read_unlock();
 
 	if (reset && idx > cb->args[0])
 		audit_log_rule_reset(table, cb->seq, idx - cb->args[0]);
 
+	rcu_read_unlock();
+
 	cb->args[0] = idx;
 	return skb->len;
 }
@@ -5760,15 +5761,15 @@ static int nf_tables_dump_set(struct sk_buff *skb, struct netlink_callback *cb)
 	if (!args.iter.err && args.iter.count == cb->args[0])
 		args.iter.err = nft_set_catchall_dump(net, skb, set,
 						      reset, cb->seq);
-	rcu_read_unlock();
-
 	nla_nest_end(skb, nest);
 	nlmsg_end(skb, nlh);
 
 	if (reset && args.iter.count > args.iter.skip)
 		audit_log_nft_set_reset(table, cb->seq,
 					args.iter.count - args.iter.skip);
 
+	rcu_read_unlock();
+
 	if (args.iter.err && args.iter.err != -EMSGSIZE)
 		return args.iter.err;
 	if (args.iter.count == cb->args[0])