Messages in this thread | | | From | Eric Dumazet <> | Date | Mon, 18 Sep 2023 09:41:15 +0200 | Subject | Re: BUG: KCSAN: data-race in rtl8169_poll |
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On Mon, Sep 18, 2023 at 8:15 AM Mirsad Todorovac <mirsad.todorovac@alu.unizg.hr> wrote: > > Hi all, > > In the vanilla torvalds tree kernel on Ubuntu 22.04, commit 6.6.0-rc1-kcsan-00269-ge789286468a9, > KCSAN discovered a data-race in rtl8169_poll(): > > [ 9591.740976] ================================================================== > [ 9591.740990] BUG: KCSAN: data-race in rtl8169_poll (drivers/net/ethernet/realtek/r8169_main.c:4430 drivers/net/ethernet/realtek/r8169_main.c:4583) r8169 > > [ 9591.741060] race at unknown origin, with read to 0xffff888109773130 of 4 bytes by interrupt on cpu 21: > [ 9591.741073] rtl8169_poll (drivers/net/ethernet/realtek/r8169_main.c:4430 drivers/net/ethernet/realtek/r8169_main.c:4583) r8169 > [ 9591.741135] __napi_poll (net/core/dev.c:6527) > [ 9591.741149] net_rx_action (net/core/dev.c:6596 net/core/dev.c:6727) > [ 9591.741161] __do_softirq (kernel/softirq.c:553) > [ 9591.741175] __irq_exit_rcu (kernel/softirq.c:427 kernel/softirq.c:632) > [ 9591.741185] irq_exit_rcu (kernel/softirq.c:647) > [ 9591.741194] common_interrupt (arch/x86/kernel/irq.c:247 (discriminator 14)) > [ 9591.741206] asm_common_interrupt (./arch/x86/include/asm/idtentry.h:636) > [ 9591.741217] cpuidle_enter_state (drivers/cpuidle/cpuidle.c:291) > [ 9591.741227] cpuidle_enter (drivers/cpuidle/cpuidle.c:390) > [ 9591.741237] call_cpuidle (kernel/sched/idle.c:135) > [ 9591.741249] do_idle (kernel/sched/idle.c:219 kernel/sched/idle.c:282) > [ 9591.741259] cpu_startup_entry (kernel/sched/idle.c:378 (discriminator 1)) > [ 9591.741268] start_secondary (arch/x86/kernel/smpboot.c:210 arch/x86/kernel/smpboot.c:294) > [ 9591.741281] secondary_startup_64_no_verify (arch/x86/kernel/head_64.S:433) > > [ 9591.741300] value changed: 0x80003fff -> 0x34044510 > > [ 9591.741314] Reported by Kernel Concurrency Sanitizer on: > [ 9591.741322] CPU: 21 PID: 0 Comm: swapper/21 Tainted: G L 6.6.0-rc1-kcsan-00269-ge789286468a9-dirty #4 > [ 9591.741334] Hardware name: ASRock X670E PG Lightning/X670E PG Lightning, BIOS 1.21 04/26/2023 > [ 9591.741343] ================================================================== > > (The taint is not from the proprietary module, but triggered from the previous reported and unfixed bug.) > > Apparently, it is this code: > > static int rtl8169_poll(struct napi_struct *napi, int budget) > { > struct rtl8169_private *tp = container_of(napi, struct rtl8169_private, napi); > struct net_device *dev = tp->dev; > int work_done; > > rtl_tx(dev, tp, budget); > > → work_done = rtl_rx(dev, tp, budget); > > if (work_done < budget && napi_complete_done(napi, work_done)) > rtl_irq_enable(tp); > > return work_done; > } > > and > > static int rtl_rx(struct net_device *dev, struct rtl8169_private *tp, int budget) > { > struct device *d = tp_to_dev(tp); > int count; > > for (count = 0; count < budget; count++, tp->cur_rx++) { > unsigned int pkt_size, entry = tp->cur_rx % NUM_RX_DESC; > struct RxDesc *desc = tp->RxDescArray + entry; > struct sk_buff *skb; > const void *rx_buf; > dma_addr_t addr; > u32 status; > > → status = le32_to_cpu(desc->opts1); > if (status & DescOwn) > break; > > /* This barrier is needed to keep us from reading > * any other fields out of the Rx descriptor until > * we know the status of DescOwn > */ > dma_rmb(); > > if (unlikely(status & RxRES)) { > . > . > . > > The reason isn't obvious, so it might be interesting if this is a valid report and whether it caused spurious corruption > of the network data on Realtek 8169 compatible cards ... >
I think this is pretty much expected.
Driver reads a piece of memory that the hardware can modify.
Adding data_race() annotations could avoid these false positives.
> Hope this helps. > > Best regards, > Mirsad Todorovac
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