4.19-stable review patch. If anyone has any objections, please let me know.
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From: Mirsad Goran Todorovac mirsad.todorovac@alu.unizg.hr
[ Upstream commit f97eee484e71890131f9c563c5cc6d5a69e4308d ]
KCSAN reported the following data-race bug:
================================================================== BUG: KCSAN: data-race in rtl8169_poll (drivers/net/ethernet/realtek/r8169_main.c:4430 drivers/net/ethernet/realtek/r8169_main.c:4583) r8169
race at unknown origin, with read to 0xffff888117e43510 of 4 bytes by interrupt on cpu 21: rtl8169_poll (drivers/net/ethernet/realtek/r8169_main.c:4430 drivers/net/ethernet/realtek/r8169_main.c:4583) 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: 0x80003fff -> 0x3402805f
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 ==================================================================
drivers/net/ethernet/realtek/r8169_main.c: ========================================== 4429 → 4430 status = le32_to_cpu(desc->opts1); 4431 if (status & DescOwn) 4432 break; 4433 4434 /* This barrier is needed to keep us from reading 4435 * any other fields out of the Rx descriptor until 4436 * we know the status of DescOwn 4437 */ 4438 dma_rmb(); 4439 4440 if (unlikely(status & RxRES)) { 4441 if (net_ratelimit()) 4442 netdev_warn(dev, "Rx ERROR. status = %08x\n",
Marco Elver explained that dma_rmb() doesn't prevent the compiler to tear up the access to desc->opts1 which can be written to concurrently. READ_ONCE() should prevent that from happening:
4429 → 4430 status = le32_to_cpu(READ_ONCE(desc->opts1)); 4431 if (status & DescOwn) 4432 break; 4433
As the consequence of this fix, this KCSAN warning was eliminated.
Fixes: 6202806e7c03a ("r8169: drop member opts1_mask from struct rtl8169_private") Suggested-by: Marco Elver elver@google.com Cc: Heiner Kallweit hkallweit1@gmail.com Cc: nic_swsd@realtek.com Cc: "David S. Miller" davem@davemloft.net Cc: Eric Dumazet edumazet@google.com Cc: Jakub Kicinski kuba@kernel.org Cc: Paolo Abeni pabeni@redhat.com Cc: netdev@vger.kernel.org Link: https://lore.kernel.org/lkml/dc7fc8fa-4ea4-e9a9-30a6-7c83e6b53188@alu.unizg.... Signed-off-by: Mirsad Goran Todorovac mirsad.todorovac@alu.unizg.hr Acked-by: Marco Elver elver@google.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/ethernet/realtek/r8169_main.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c index b7bba00ab4587..92875a935eb13 100644 --- a/drivers/net/ethernet/realtek/r8169_main.c +++ b/drivers/net/ethernet/realtek/r8169_main.c @@ -6541,7 +6541,7 @@ static int rtl_rx(struct net_device *dev, struct rtl8169_private *tp, u32 budget struct RxDesc *desc = tp->RxDescArray + entry; u32 status;
- status = le32_to_cpu(desc->opts1); + status = le32_to_cpu(READ_ONCE(desc->opts1)); if (status & DescOwn) break;