From: Eric Dumazet edumazet@google.com
[ Upstream commit 4a2b285e7e103d4d6c6ed3e5052a0ff74a5d7f15 ]
Fix the data-race reported by syzbot [1] Issue here is that igmp_ifc_timer_expire() can update in_dev->mr_ifc_count while another change just occured from another context.
in_dev->mr_ifc_count is only 8bit wide, so the race had little consequences.
[1] BUG: KCSAN: data-race in igmp_ifc_event / igmp_ifc_timer_expire
write to 0xffff8881051e3062 of 1 bytes by task 12547 on cpu 0: igmp_ifc_event+0x1d5/0x290 net/ipv4/igmp.c:821 igmp_group_added+0x462/0x490 net/ipv4/igmp.c:1356 ____ip_mc_inc_group+0x3ff/0x500 net/ipv4/igmp.c:1461 __ip_mc_join_group+0x24d/0x2c0 net/ipv4/igmp.c:2199 ip_mc_join_group_ssm+0x20/0x30 net/ipv4/igmp.c:2218 do_ip_setsockopt net/ipv4/ip_sockglue.c:1285 [inline] ip_setsockopt+0x1827/0x2a80 net/ipv4/ip_sockglue.c:1423 tcp_setsockopt+0x8c/0xa0 net/ipv4/tcp.c:3657 sock_common_setsockopt+0x5d/0x70 net/core/sock.c:3362 __sys_setsockopt+0x18f/0x200 net/socket.c:2159 __do_sys_setsockopt net/socket.c:2170 [inline] __se_sys_setsockopt net/socket.c:2167 [inline] __x64_sys_setsockopt+0x62/0x70 net/socket.c:2167 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae
read to 0xffff8881051e3062 of 1 bytes by interrupt on cpu 1: igmp_ifc_timer_expire+0x706/0xa30 net/ipv4/igmp.c:808 call_timer_fn+0x2e/0x1d0 kernel/time/timer.c:1419 expire_timers+0x135/0x250 kernel/time/timer.c:1464 __run_timers+0x358/0x420 kernel/time/timer.c:1732 run_timer_softirq+0x19/0x30 kernel/time/timer.c:1745 __do_softirq+0x12c/0x26e kernel/softirq.c:558 invoke_softirq kernel/softirq.c:432 [inline] __irq_exit_rcu+0x9a/0xb0 kernel/softirq.c:636 sysvec_apic_timer_interrupt+0x69/0x80 arch/x86/kernel/apic/apic.c:1100 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:638 console_unlock+0x8e8/0xb30 kernel/printk/printk.c:2646 vprintk_emit+0x125/0x3d0 kernel/printk/printk.c:2174 vprintk_default+0x22/0x30 kernel/printk/printk.c:2185 vprintk+0x15a/0x170 kernel/printk/printk_safe.c:392 printk+0x62/0x87 kernel/printk/printk.c:2216 selinux_netlink_send+0x399/0x400 security/selinux/hooks.c:6041 security_netlink_send+0x42/0x90 security/security.c:2070 netlink_sendmsg+0x59e/0x7c0 net/netlink/af_netlink.c:1919 sock_sendmsg_nosec net/socket.c:703 [inline] sock_sendmsg net/socket.c:723 [inline] ____sys_sendmsg+0x360/0x4d0 net/socket.c:2392 ___sys_sendmsg net/socket.c:2446 [inline] __sys_sendmsg+0x1ed/0x270 net/socket.c:2475 __do_sys_sendmsg net/socket.c:2484 [inline] __se_sys_sendmsg net/socket.c:2482 [inline] __x64_sys_sendmsg+0x42/0x50 net/socket.c:2482 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae
value changed: 0x01 -> 0x02
Reported by Kernel Concurrency Sanitizer on: CPU: 1 PID: 12539 Comm: syz-executor.1 Not tainted 5.14.0-rc4-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/ipv4/igmp.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-)
diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c index 6b3c558a4f23..a51360087b19 100644 --- a/net/ipv4/igmp.c +++ b/net/ipv4/igmp.c @@ -803,10 +803,17 @@ static void igmp_gq_timer_expire(struct timer_list *t) static void igmp_ifc_timer_expire(struct timer_list *t) { struct in_device *in_dev = from_timer(in_dev, t, mr_ifc_timer); + u8 mr_ifc_count;
igmpv3_send_cr(in_dev); - if (in_dev->mr_ifc_count) { - in_dev->mr_ifc_count--; +restart: + mr_ifc_count = READ_ONCE(in_dev->mr_ifc_count); + + if (mr_ifc_count) { + if (cmpxchg(&in_dev->mr_ifc_count, + mr_ifc_count, + mr_ifc_count - 1) != mr_ifc_count) + goto restart; igmp_ifc_start_timer(in_dev, unsolicited_report_interval(in_dev)); } @@ -818,7 +825,7 @@ static void igmp_ifc_event(struct in_device *in_dev) struct net *net = dev_net(in_dev->dev); if (IGMP_V1_SEEN(in_dev) || IGMP_V2_SEEN(in_dev)) return; - in_dev->mr_ifc_count = in_dev->mr_qrv ?: net->ipv4.sysctl_igmp_qrv; + WRITE_ONCE(in_dev->mr_ifc_count, in_dev->mr_qrv ?: net->ipv4.sysctl_igmp_qrv); igmp_ifc_start_timer(in_dev, 1); }
@@ -957,7 +964,7 @@ static bool igmp_heard_query(struct in_device *in_dev, struct sk_buff *skb, in_dev->mr_qri; } /* cancel the interface change timer */ - in_dev->mr_ifc_count = 0; + WRITE_ONCE(in_dev->mr_ifc_count, 0); if (del_timer(&in_dev->mr_ifc_timer)) __in_dev_put(in_dev); /* clear deleted report items */ @@ -1724,7 +1731,7 @@ void ip_mc_down(struct in_device *in_dev) igmp_group_dropped(pmc);
#ifdef CONFIG_IP_MULTICAST - in_dev->mr_ifc_count = 0; + WRITE_ONCE(in_dev->mr_ifc_count, 0); if (del_timer(&in_dev->mr_ifc_timer)) __in_dev_put(in_dev); in_dev->mr_gq_running = 0; @@ -1941,7 +1948,7 @@ static int ip_mc_del_src(struct in_device *in_dev, __be32 *pmca, int sfmode, pmc->sfmode = MCAST_INCLUDE; #ifdef CONFIG_IP_MULTICAST pmc->crcount = in_dev->mr_qrv ?: net->ipv4.sysctl_igmp_qrv; - in_dev->mr_ifc_count = pmc->crcount; + WRITE_ONCE(in_dev->mr_ifc_count, pmc->crcount); for (psf = pmc->sources; psf; psf = psf->sf_next) psf->sf_crcount = 0; igmp_ifc_event(pmc->interface); @@ -2120,7 +2127,7 @@ static int ip_mc_add_src(struct in_device *in_dev, __be32 *pmca, int sfmode, /* else no filters; keep old mode for reports */
pmc->crcount = in_dev->mr_qrv ?: net->ipv4.sysctl_igmp_qrv; - in_dev->mr_ifc_count = pmc->crcount; + WRITE_ONCE(in_dev->mr_ifc_count, pmc->crcount); for (psf = pmc->sources; psf; psf = psf->sf_next) psf->sf_crcount = 0; igmp_ifc_event(in_dev);