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Message-ID: <20231017200138.GB1940501@kernel.org> Date: Tue, 17 Oct 2023 22:01:38 +0200 From: Simon Horman <horms@...nel.org> To: Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr> Cc: Heiner Kallweit <hkallweit1@...il.com>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, nic_swsd@...ltek.com, "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Marco Elver <elver@...gle.com> Subject: Re: [PATCH v2 3/3] r8169: fix the KCSAN reported data-race in rtl_tx while reading TxDescArray[entry].opts1 On Mon, Oct 16, 2023 at 11:47:56PM +0200, Mirsad Goran Todorovac wrote: > KCSAN reported the following data-race: > > ================================================================== > BUG: KCSAN: data-race in rtl8169_poll (drivers/net/ethernet/realtek/r8169_main.c:4368 drivers/net/ethernet/realtek/r8169_main.c:4581) r8169 > > race at unknown origin, with read to 0xffff888140d37570 of 4 bytes by interrupt on cpu 21: > rtl8169_poll (drivers/net/ethernet/realtek/r8169_main.c:4368 drivers/net/ethernet/realtek/r8169_main.c:4581) r8169 > __napi_poll (net/core/dev.c:6527) > net_rx_action (net/core/dev.c:6596 net/core/dev.c:6727) > __do_softirq (kernel/softirq.c:553) > __irq_exit_rcu (kernel/softirq.c:427 kernel/softirq.c:632) > irq_exit_rcu (kernel/softirq.c:647) > sysvec_apic_timer_interrupt (arch/x86/kernel/apic/apic.c:1074 (discriminator 14)) > asm_sysvec_apic_timer_interrupt (./arch/x86/include/asm/idtentry.h:645) > cpuidle_enter_state (drivers/cpuidle/cpuidle.c:291) > cpuidle_enter (drivers/cpuidle/cpuidle.c:390) > call_cpuidle (kernel/sched/idle.c:135) > do_idle (kernel/sched/idle.c:219 kernel/sched/idle.c:282) > cpu_startup_entry (kernel/sched/idle.c:378 (discriminator 1)) > start_secondary (arch/x86/kernel/smpboot.c:210 arch/x86/kernel/smpboot.c:294) > secondary_startup_64_no_verify (arch/x86/kernel/head_64.S:433) > > value changed: 0xb0000042 -> 0x00000000 > > Reported by Kernel Concurrency Sanitizer on: > CPU: 21 PID: 0 Comm: swapper/21 Tainted: G L 6.6.0-rc2-kcsan-00143-gb5cbe7c00aa0 #41 > Hardware name: ASRock X670E PG Lightning/X670E PG Lightning, BIOS 1.21 04/26/2023 > ================================================================== > > The read side is in > > drivers/net/ethernet/realtek/r8169_main.c > ========================================= > 4355 static void rtl_tx(struct net_device *dev, struct rtl8169_private *tp, > 4356 int budget) > 4357 { > 4358 unsigned int dirty_tx, bytes_compl = 0, pkts_compl = 0; > 4359 struct sk_buff *skb; > 4360 > 4361 dirty_tx = tp->dirty_tx; > 4362 > 4363 while (READ_ONCE(tp->cur_tx) != dirty_tx) { > 4364 unsigned int entry = dirty_tx % NUM_TX_DESC; > 4365 u32 status; > 4366 > → 4367 status = le32_to_cpu(tp->TxDescArray[entry].opts1); > 4368 if (status & DescOwn) > 4369 break; > 4370 > 4371 skb = tp->tx_skb[entry].skb; > 4372 rtl8169_unmap_tx_skb(tp, entry); > 4373 > 4374 if (skb) { > 4375 pkts_compl++; > 4376 bytes_compl += skb->len; > 4377 napi_consume_skb(skb, budget); > 4378 } > 4379 dirty_tx++; > 4380 } > 4381 > 4382 if (tp->dirty_tx != dirty_tx) { > 4383 dev_sw_netstats_tx_add(dev, pkts_compl, bytes_compl); > 4384 WRITE_ONCE(tp->dirty_tx, dirty_tx); > 4385 > 4386 netif_subqueue_completed_wake(dev, 0, pkts_compl, bytes_compl, > 4387 rtl_tx_slots_avail(tp), > 4388 R8169_TX_START_THRS); > 4389 /* > 4390 * 8168 hack: TxPoll requests are lost when the Tx packets are > 4391 * too close. Let's kick an extra TxPoll request when a burst > 4392 * of start_xmit activity is detected (if it is not detected, > 4393 * it is slow enough). -- FR > 4394 * If skb is NULL then we come here again once a tx irq is > 4395 * triggered after the last fragment is marked transmitted. > 4396 */ > 4397 if (READ_ONCE(tp->cur_tx) != dirty_tx && skb) > 4398 rtl8169_doorbell(tp); > 4399 } > 4400 } > > tp->TxDescArray[entry].opts1 is reported to have a data-race and READ_ONCE() fixes > this KCSAN warning. > > 4366 > → 4367 status = le32_to_cpu(READ_ONCE(tp->TxDescArray[entry].opts1)); > 4368 if (status & DescOwn) > 4369 break; > 4370 > > Fixes: ^1da177e4c3f4 ("initial git repository build") Hi Mirsad, The fixes tag above seems wrong. > Cc: Heiner Kallweit <hkallweit1@...il.com> > Cc: nic_swsd@...ltek.com > Cc: "David S. Miller" <davem@...emloft.net> > Cc: Eric Dumazet <edumazet@...gle.com> > Cc: Jakub Kicinski <kuba@...nel.org> > Cc: Paolo Abeni <pabeni@...hat.com> > Cc: Marco Elver <elver@...gle.com> > Cc: netdev@...r.kernel.org > Link: https://lore.kernel.org/lkml/dc7fc8fa-4ea4-e9a9-30a6-7c83e6b53188@alu.unizg.hr/ > Signed-off-by: Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr> > Acked-by: Marco Elver <elver@...gle.com> ...
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