[PATCH 4.9 16/31] net/packet: refine check for priv area size

From: Greg Kroah-Hartman
Date: Tue Jun 12 2018 - 13:04:35 EST

4.9-stable review patch. If anyone has any objections, please let me know.


From: Eric Dumazet <edumazet@xxxxxxxxxx>

[ Upstream commit eb73190f4fbeedf762394e92d6a4ec9ace684c88 ]

syzbot was able to trick af_packet again [1]

Various commits tried to address the problem in the past,
but failed to take into account V3 header size.


tpacket_rcv: packet too big, clamped from 72 to 4294967224. macoff=96
BUG: KASAN: use-after-free in prb_run_all_ft_ops net/packet/af_packet.c:1016 [inline]
BUG: KASAN: use-after-free in prb_fill_curr_block.isra.59+0x4e5/0x5c0 net/packet/af_packet.c:1039
Write of size 2 at addr ffff8801cb62000e by task kworker/1:2/2106

CPU: 1 PID: 2106 Comm: kworker/1:2 Not tainted 4.17.0-rc7+ #77
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: ipv6_addrconf addrconf_dad_work
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1b9/0x294 lib/dump_stack.c:113
print_address_description+0x6c/0x20b mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
__asan_report_store2_noabort+0x17/0x20 mm/kasan/report.c:436
prb_run_all_ft_ops net/packet/af_packet.c:1016 [inline]
prb_fill_curr_block.isra.59+0x4e5/0x5c0 net/packet/af_packet.c:1039
__packet_lookup_frame_in_block net/packet/af_packet.c:1094 [inline]
packet_current_rx_frame net/packet/af_packet.c:1117 [inline]
tpacket_rcv+0x1866/0x3340 net/packet/af_packet.c:2282
dev_queue_xmit_nit+0x891/0xb90 net/core/dev.c:2018
xmit_one net/core/dev.c:3049 [inline]
dev_hard_start_xmit+0x16b/0xc10 net/core/dev.c:3069
__dev_queue_xmit+0x2724/0x34c0 net/core/dev.c:3584
dev_queue_xmit+0x17/0x20 net/core/dev.c:3617
neigh_resolve_output+0x679/0xad0 net/core/neighbour.c:1358
neigh_output include/net/neighbour.h:482 [inline]
ip6_finish_output2+0xc9c/0x2810 net/ipv6/ip6_output.c:120
ip6_finish_output+0x5fe/0xbc0 net/ipv6/ip6_output.c:154
NF_HOOK_COND include/linux/netfilter.h:277 [inline]
ip6_output+0x227/0x9b0 net/ipv6/ip6_output.c:171
dst_output include/net/dst.h:444 [inline]
NF_HOOK include/linux/netfilter.h:288 [inline]
ndisc_send_skb+0x100d/0x1570 net/ipv6/ndisc.c:491
ndisc_send_ns+0x3c1/0x8d0 net/ipv6/ndisc.c:633
addrconf_dad_work+0xbef/0x1340 net/ipv6/addrconf.c:4033
process_one_work+0xc1e/0x1b50 kernel/workqueue.c:2145
worker_thread+0x1cc/0x1440 kernel/workqueue.c:2279
kthread+0x345/0x410 kernel/kthread.c:240
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412

The buggy address belongs to the page:
page:ffffea00072d8800 count:0 mapcount:-127 mapping:0000000000000000 index:0xffff8801cb620e80
flags: 0x2fffc0000000000()
raw: 02fffc0000000000 0000000000000000 ffff8801cb620e80 00000000ffffff80
raw: ffffea00072e3820 ffffea0007132d20 0000000000000002 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801cb61ff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8801cb61ff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8801cb620000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff8801cb620080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff8801cb620100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff

Fixes: 2b6867c2ce76 ("net/packet: fix overflow in check for priv area size")
Fixes: dc808110bb62 ("packet: handle too big packets for PACKET_V3")
Fixes: f6fb8f100b80 ("af-packet: TPACKET_V3 flexible buffer implementation.")
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
net/packet/af_packet.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -4299,7 +4299,7 @@ static int packet_set_ring(struct sock *
goto out;
if (po->tp_version >= TPACKET_V3 &&
req->tp_block_size <=
- BLK_PLUS_PRIV((u64)req_u->req3.tp_sizeof_priv))
+ BLK_PLUS_PRIV((u64)req_u->req3.tp_sizeof_priv) + sizeof(struct tpacket3_hdr))
goto out;
if (unlikely(req->tp_frame_size < po->tp_hdrlen +