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From:   Jia-Ju Bai <baijiaju1990@gmail.com>
To:     jingoohan1@gmail.com, Joao.Pinto@synopsys.com,
        lorenzo.pieralisi@arm.com, bhelgaas@google.com
Cc:     linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
        Jia-Ju Bai <baijiaju1990@gmail.com>
Subject: [PATCH] pci: dwc: pcie_designware: Fix a sleep-in-atomic-context bug in dw_pcie_prog_outbound_atu
Date:   Sun,  2 Sep 2018 11:38:11 +0800
Message-Id: <20180902033811.26858-1-baijiaju1990@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

The driver may sleep with holding a spinlock and in an interupt handler.

The function call paths (from bottom to top) in Linux-4.16 are:

[FUNC] usleep_range
drivers/pci/dwc/pcie-designware.c, 181: 
	usleep_range in dw_pcie_prog_outbound_atu
drivers/pci/dwc/pcie-designware-host.c, 479: 
	dw_pcie_prog_outbound_atu in dw_pcie_rd_other_conf
drivers/pci/dwc/pcie-designware-host.c, 561: 
	dw_pcie_rd_other_conf in dw_pcie_rd_conf
drivers/pci/access.c, 66: 
	[FUNC_PTR]dw_pcie_rd_conf in pci_bus_read_config_word
drivers/pci/access.c, 918: 
	pci_bus_read_config_word in pci_read_config_word
drivers/block/umem.c, 630: 
	pci_read_config_word in mm_interrupt (interrupt handler)

[FUNC] usleep_range
drivers/pci/dwc/pcie-designware.c, 181: 
	usleep_range in dw_pcie_prog_outbound_atu
drivers/pci/dwc/pcie-designware-host.c, 479: 
	dw_pcie_prog_outbound_atu in dw_pcie_rd_other_conf
drivers/pci/dwc/pcie-designware-host.c, 561: 
	dw_pcie_rd_other_conf in dw_pcie_rd_conf
drivers/pci/access.c, 66: 
	[FUNC_PTR]dw_pcie_rd_conf in pci_bus_read_config_word
drivers/pci/access.c, 918: 
	pci_bus_read_config_word in pci_read_config_word
drivers/ata/pata_efar.c, 115: 
	pci_read_config_word in efar_set_piomode
drivers/ata/pata_efar.c, 113: 
	_raw_spin_lock_irqsave in efar_set_piomod

[FUNC] usleep_range
drivers/pci/dwc/pcie-designware.c, 181: 
	usleep_range in dw_pcie_prog_outbound_atu
drivers/pci/dwc/pcie-designware-host.c, 479: 
	dw_pcie_prog_outbound_atu in dw_pcie_rd_other_conf
drivers/pci/dwc/pcie-designware-host.c, 561: 
	dw_pcie_rd_other_conf in dw_pcie_rd_conf
drivers/pci/access.c, 66: 
	[FUNC_PTR]dw_pcie_rd_conf in pci_bus_read_config_word
drivers/pci/access.c, 918: 
	pci_bus_read_config_word in pci_read_config_word
drivers/block/mtip32xx/mtip32xx.c, 158: 
	pci_read_config_word in mtip_check_surprise_removal
drivers/block/mtip32xx/mtip32xx.c, 843: 
	mtip_check_surprise_removal in mtip_handle_irq
drivers/block/mtip32xx/mtip32xx.c, 879: 
	mtip_handle_irq in mtip_irq_handler (interrupt handler)

[FUNC] usleep_range
drivers/pci/dwc/pcie-designware.c, 181: 
	usleep_range in dw_pcie_prog_outbound_atu
drivers/pci/dwc/pcie-designware-host.c, 479: 
	dw_pcie_prog_outbound_atu in dw_pcie_rd_other_conf
drivers/pci/dwc/pcie-designware-host.c, 561: 
	dw_pcie_rd_other_conf in dw_pcie_rd_conf
drivers/pci/access.c, 66: 
	[FUNC_PTR]dw_pcie_rd_conf in pci_bus_read_config_word
drivers/pci/access.c, 918: 
	pci_bus_read_config_word in pci_read_config_word
drivers/gpu/vga/vgaarb.c, 645: 
	pci_read_config_word in vga_arbiter_add_pci_device
drivers/gpu/vga/vgaarb.c, 629: 
	_raw_spin_lock_irqsave in vga_arbiter_add_pci_device

[FUNC] usleep_range
drivers/pci/dwc/pcie-designware.c, 181: 
	usleep_range in dw_pcie_prog_outbound_atu
drivers/pci/dwc/pcie-designware-host.c, 479: 
	dw_pcie_prog_outbound_atu in dw_pcie_rd_other_conf
drivers/pci/dwc/pcie-designware-host.c, 561: 
	dw_pcie_rd_other_conf in dw_pcie_rd_conf
drivers/pci/access.c, 66: 
	[FUNC_PTR]dw_pcie_rd_conf in pci_bus_read_config_word
drivers/pci/access.c, 918: 
	pci_bus_read_config_word in pci_read_config_word
drivers/pci/ats.c, 139: 
	pci_read_config_word in pci_ats_queue_depth
drivers/iommu/intel-iommu.c, 1519: 
	pci_ats_queue_depth in iommu_enable_dev_iotlb
drivers/iommu/intel-iommu.c, 5295: 
	iommu_enable_dev_iotlb in intel_iommu_enable_pasid
drivers/iommu/intel-iommu.c, 5241: 
	_raw_spin_lock_irqsave in intel_iommu_enable_pasid

To fix this bug, usleep_range() is replaced with udelay().

This bug is found by my static analysis tool DSAC.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
 drivers/pci/controller/dwc/pcie-designware.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index 778c4f76a884..7f50f7e51543 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -135,7 +135,7 @@ static void dw_pcie_prog_outbound_atu_unroll(struct dw_pcie *pci, int index,
 		if (val & PCIE_ATU_ENABLE)
 			return;
 
-		usleep_range(LINK_WAIT_IATU_MIN, LINK_WAIT_IATU_MAX);
+		udelay(LINK_WAIT_IATU_MAX);
 	}
 	dev_err(pci->dev, "Outbound iATU is not being enabled\n");
 }
-- 
2.17.0