This is a note to let you know that I've just added the patch titled inetpeer: fix data-race in inet_putpeer / inet_putpeer to the 4.19-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: inetpeer-fix-data-race-in-inet_putpeer-inet_putpeer.patch and it can be found in the queue-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 71685eb4ce80ae9c49eff82ca4dd15acab215de9 Mon Sep 17 00:00:00 2001 From: Eric Dumazet <edumazet@xxxxxxxxxx> Date: Thu, 7 Nov 2019 10:30:42 -0800 Subject: inetpeer: fix data-race in inet_putpeer / inet_putpeer From: Eric Dumazet <edumazet@xxxxxxxxxx> commit 71685eb4ce80ae9c49eff82ca4dd15acab215de9 upstream. We need to explicitely forbid read/store tearing in inet_peer_gc() and inet_putpeer(). The following syzbot report reminds us about inet_putpeer() running without a lock held. BUG: KCSAN: data-race in inet_putpeer / inet_putpeer write to 0xffff888121fb2ed0 of 4 bytes by interrupt on cpu 0: inet_putpeer+0x37/0xa0 net/ipv4/inetpeer.c:240 ip4_frag_free+0x3d/0x50 net/ipv4/ip_fragment.c:102 inet_frag_destroy_rcu+0x58/0x80 net/ipv4/inet_fragment.c:228 __rcu_reclaim kernel/rcu/rcu.h:222 [inline] rcu_do_batch+0x256/0x5b0 kernel/rcu/tree.c:2157 rcu_core+0x369/0x4d0 kernel/rcu/tree.c:2377 rcu_core_si+0x12/0x20 kernel/rcu/tree.c:2386 __do_softirq+0x115/0x33f kernel/softirq.c:292 invoke_softirq kernel/softirq.c:373 [inline] irq_exit+0xbb/0xe0 kernel/softirq.c:413 exiting_irq arch/x86/include/asm/apic.h:536 [inline] smp_apic_timer_interrupt+0xe6/0x280 arch/x86/kernel/apic/apic.c:1137 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:830 native_safe_halt+0xe/0x10 arch/x86/kernel/paravirt.c:71 arch_cpu_idle+0x1f/0x30 arch/x86/kernel/process.c:571 default_idle_call+0x1e/0x40 kernel/sched/idle.c:94 cpuidle_idle_call kernel/sched/idle.c:154 [inline] do_idle+0x1af/0x280 kernel/sched/idle.c:263 write to 0xffff888121fb2ed0 of 4 bytes by interrupt on cpu 1: inet_putpeer+0x37/0xa0 net/ipv4/inetpeer.c:240 ip4_frag_free+0x3d/0x50 net/ipv4/ip_fragment.c:102 inet_frag_destroy_rcu+0x58/0x80 net/ipv4/inet_fragment.c:228 __rcu_reclaim kernel/rcu/rcu.h:222 [inline] rcu_do_batch+0x256/0x5b0 kernel/rcu/tree.c:2157 rcu_core+0x369/0x4d0 kernel/rcu/tree.c:2377 rcu_core_si+0x12/0x20 kernel/rcu/tree.c:2386 __do_softirq+0x115/0x33f kernel/softirq.c:292 run_ksoftirqd+0x46/0x60 kernel/softirq.c:603 smpboot_thread_fn+0x37d/0x4a0 kernel/smpboot.c:165 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352 Reported by Kernel Concurrency Sanitizer on: CPU: 1 PID: 16 Comm: ksoftirqd/1 Not tainted 5.4.0-rc3+ #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Fixes: 4b9d9be839fd ("inetpeer: remove unused list") 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/ipv4/inetpeer.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) --- a/net/ipv4/inetpeer.c +++ b/net/ipv4/inetpeer.c @@ -160,7 +160,12 @@ static void inet_peer_gc(struct inet_pee base->total / inet_peer_threshold * HZ; for (i = 0; i < gc_cnt; i++) { p = gc_stack[i]; - delta = (__u32)jiffies - p->dtime; + + /* The READ_ONCE() pairs with the WRITE_ONCE() + * in inet_putpeer() + */ + delta = (__u32)jiffies - READ_ONCE(p->dtime); + if (delta < ttl || !refcount_dec_if_one(&p->refcnt)) gc_stack[i] = NULL; } @@ -237,7 +242,10 @@ EXPORT_SYMBOL_GPL(inet_getpeer); void inet_putpeer(struct inet_peer *p) { - p->dtime = (__u32)jiffies; + /* The WRITE_ONCE() pairs with itself (we run lockless) + * and the READ_ONCE() in inet_peer_gc() + */ + WRITE_ONCE(p->dtime, (__u32)jiffies); if (refcount_dec_and_test(&p->refcnt)) call_rcu(&p->rcu, inetpeer_free_rcu); Patches currently in stable-queue which might be from edumazet@xxxxxxxxxx are queue-4.19/net-icmp-fix-data-race-in-cmp_global_allow.patch queue-4.19/dma-debug-add-a-schedule-point-in-debug_dma_dump_map.patch queue-4.19/net-add-a-read_once-in-skb_peek_tail.patch queue-4.19/inetpeer-fix-data-race-in-inet_putpeer-inet_putpeer.patch queue-4.19/netfilter-bridge-make-sure-to-pull-arp-header-in-br_nf_forward_arp.patch queue-4.19/6pack-mkiss-fix-possible-deadlock.patch queue-4.19/hrtimer-annotate-lockless-access-to-timer-state.patch