diff options
author | Eric Dumazet <edumazet@google.com> | 2019-11-08 16:07:46 +0300 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2019-11-09 01:06:19 +0300 |
commit | b756ad928d98e5ef0b74af7546a6a31a8dadde00 (patch) | |
tree | cc0f3e442a8f1340158782365bd470bc38ea7596 /net/packet/af_packet.c | |
parent | 1c8f11d057d61d9039a55545124ecb4248c6e625 (diff) | |
download | linux-b756ad928d98e5ef0b74af7546a6a31a8dadde00.tar.xz |
packet: fix data-race in fanout_flow_is_huge()
KCSAN reported the following data-race [1]
Adding a couple of READ_ONCE()/WRITE_ONCE() should silence it.
Since the report hinted about multiple cpus using the history
concurrently, I added a test avoiding writing on it if the
victim slot already contains the desired value.
[1]
BUG: KCSAN: data-race in fanout_demux_rollover / fanout_demux_rollover
read to 0xffff8880b01786cc of 4 bytes by task 18921 on cpu 1:
fanout_flow_is_huge net/packet/af_packet.c:1303 [inline]
fanout_demux_rollover+0x33e/0x3f0 net/packet/af_packet.c:1353
packet_rcv_fanout+0x34e/0x490 net/packet/af_packet.c:1453
deliver_skb net/core/dev.c:1888 [inline]
dev_queue_xmit_nit+0x15b/0x540 net/core/dev.c:1958
xmit_one net/core/dev.c:3195 [inline]
dev_hard_start_xmit+0x3f5/0x430 net/core/dev.c:3215
__dev_queue_xmit+0x14ab/0x1b40 net/core/dev.c:3792
dev_queue_xmit+0x21/0x30 net/core/dev.c:3825
neigh_direct_output+0x1f/0x30 net/core/neighbour.c:1530
neigh_output include/net/neighbour.h:511 [inline]
ip6_finish_output2+0x7a2/0xec0 net/ipv6/ip6_output.c:116
__ip6_finish_output net/ipv6/ip6_output.c:142 [inline]
__ip6_finish_output+0x2d7/0x330 net/ipv6/ip6_output.c:127
ip6_finish_output+0x41/0x160 net/ipv6/ip6_output.c:152
NF_HOOK_COND include/linux/netfilter.h:294 [inline]
ip6_output+0xf2/0x280 net/ipv6/ip6_output.c:175
dst_output include/net/dst.h:436 [inline]
ip6_local_out+0x74/0x90 net/ipv6/output_core.c:179
ip6_send_skb+0x53/0x110 net/ipv6/ip6_output.c:1795
udp_v6_send_skb.isra.0+0x3ec/0xa70 net/ipv6/udp.c:1173
udpv6_sendmsg+0x1906/0x1c20 net/ipv6/udp.c:1471
inet6_sendmsg+0x6d/0x90 net/ipv6/af_inet6.c:576
sock_sendmsg_nosec net/socket.c:637 [inline]
sock_sendmsg+0x9f/0xc0 net/socket.c:657
___sys_sendmsg+0x2b7/0x5d0 net/socket.c:2311
__sys_sendmmsg+0x123/0x350 net/socket.c:2413
__do_sys_sendmmsg net/socket.c:2442 [inline]
__se_sys_sendmmsg net/socket.c:2439 [inline]
__x64_sys_sendmmsg+0x64/0x80 net/socket.c:2439
do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x44/0xa9
write to 0xffff8880b01786cc of 4 bytes by task 18922 on cpu 0:
fanout_flow_is_huge net/packet/af_packet.c:1306 [inline]
fanout_demux_rollover+0x3a4/0x3f0 net/packet/af_packet.c:1353
packet_rcv_fanout+0x34e/0x490 net/packet/af_packet.c:1453
deliver_skb net/core/dev.c:1888 [inline]
dev_queue_xmit_nit+0x15b/0x540 net/core/dev.c:1958
xmit_one net/core/dev.c:3195 [inline]
dev_hard_start_xmit+0x3f5/0x430 net/core/dev.c:3215
__dev_queue_xmit+0x14ab/0x1b40 net/core/dev.c:3792
dev_queue_xmit+0x21/0x30 net/core/dev.c:3825
neigh_direct_output+0x1f/0x30 net/core/neighbour.c:1530
neigh_output include/net/neighbour.h:511 [inline]
ip6_finish_output2+0x7a2/0xec0 net/ipv6/ip6_output.c:116
__ip6_finish_output net/ipv6/ip6_output.c:142 [inline]
__ip6_finish_output+0x2d7/0x330 net/ipv6/ip6_output.c:127
ip6_finish_output+0x41/0x160 net/ipv6/ip6_output.c:152
NF_HOOK_COND include/linux/netfilter.h:294 [inline]
ip6_output+0xf2/0x280 net/ipv6/ip6_output.c:175
dst_output include/net/dst.h:436 [inline]
ip6_local_out+0x74/0x90 net/ipv6/output_core.c:179
ip6_send_skb+0x53/0x110 net/ipv6/ip6_output.c:1795
udp_v6_send_skb.isra.0+0x3ec/0xa70 net/ipv6/udp.c:1173
udpv6_sendmsg+0x1906/0x1c20 net/ipv6/udp.c:1471
inet6_sendmsg+0x6d/0x90 net/ipv6/af_inet6.c:576
sock_sendmsg_nosec net/socket.c:637 [inline]
sock_sendmsg+0x9f/0xc0 net/socket.c:657
___sys_sendmsg+0x2b7/0x5d0 net/socket.c:2311
__sys_sendmmsg+0x123/0x350 net/socket.c:2413
__do_sys_sendmmsg net/socket.c:2442 [inline]
__se_sys_sendmmsg net/socket.c:2439 [inline]
__x64_sys_sendmmsg+0x64/0x80 net/socket.c:2439
do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x44/0xa9
Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 18922 Comm: syz-executor.3 Not tainted 5.4.0-rc6+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Fixes: 3b3a5b0aab5b ("packet: rollover huge flows before small flows")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/packet/af_packet.c')
-rw-r--r-- | net/packet/af_packet.c | 12 |
1 files changed, 9 insertions, 3 deletions
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 82a50e850245..53c1d41fb1c9 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1295,15 +1295,21 @@ static void packet_sock_destruct(struct sock *sk) static bool fanout_flow_is_huge(struct packet_sock *po, struct sk_buff *skb) { - u32 rxhash; + u32 *history = po->rollover->history; + u32 victim, rxhash; int i, count = 0; rxhash = skb_get_hash(skb); for (i = 0; i < ROLLOVER_HLEN; i++) - if (po->rollover->history[i] == rxhash) + if (READ_ONCE(history[i]) == rxhash) count++; - po->rollover->history[prandom_u32() % ROLLOVER_HLEN] = rxhash; + victim = prandom_u32() % ROLLOVER_HLEN; + + /* Avoid dirtying the cache line if possible */ + if (READ_ONCE(history[victim]) != rxhash) + WRITE_ONCE(history[victim], rxhash); + return count > (ROLLOVER_HLEN >> 1); } |