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authorEric Dumazet <edumazet@google.com>2019-11-08 05:07:46 -0800
committerDavid S. Miller <davem@davemloft.net>2019-11-08 14:06:19 -0800
commitb756ad928d98e5ef0b74af7546a6a31a8dadde00 (patch)
treecc0f3e442a8f1340158782365bd470bc38ea7596 /net/packet
parentMerge branch 'TIPC-Encryption' (diff)
downloadlinux-dev-b756ad928d98e5ef0b74af7546a6a31a8dadde00.tar.xz
linux-dev-b756ad928d98e5ef0b74af7546a6a31a8dadde00.zip
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')
-rw-r--r--net/packet/af_packet.c12
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);
}