linux-kernel - [PATCH v1] PCI: imx6: Handle the abort from user-space

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Date:   Mon, 31 Jan 2022 08:52:35 +0100
From:   Francesco Dolcini <francesco.dolcini@...adex.com>
To:     Richard Zhu <hongxing.zhu@....com>,
        Lucas Stach <l.stach@...gutronix.de>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Jason Liu <jason.hui.liu@....com>
Cc:     linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Francesco Dolcini <francesco.dolcini@...adex.com>
Subject: [PATCH v1] PCI: imx6: Handle the abort from user-space

From: Jason Liu <jason.hui.liu@....com>

The driver install one hook to handle the external abort, but issue
is that if the abort introduced from user space code, the following
code unsigned long instr = *(unsigned long *)pc; which will created
another data-abort(page domain fault) if CONFIG_CPU_SW_DOMAIN_PAN.

The patch does not intent to use copy_from_user and then do the hack
due to the security consideration. In fact, we can just return and
report the external abort to user-space.

Link: https://lore.kernel.org/all/20220128082920.591115-1-francesco.dolcini@toradex.com
Signed-off-by: Jason Liu <jason.hui.liu@....com>
Reviewed-by: Richard Zhu <hongxing.zhu@....com>
Signed-off-by: Francesco Dolcini <francesco.dolcini@...adex.com>
Acked-by: Lucas Stach <l.stach@...gutronix.de>
---
rfc -> v1:
 * added Acked-by Lucas Stach
 * include correct header for user_mode()
---
 drivers/pci/controller/dwc/pci-imx6.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
index 6974bd5aa116..c47a05332a94 100644
--- a/drivers/pci/controller/dwc/pci-imx6.c
+++ b/drivers/pci/controller/dwc/pci-imx6.c
@@ -22,6 +22,7 @@
 #include <linux/of_address.h>
 #include <linux/pci.h>
 #include <linux/platform_device.h>
+#include <linux/ptrace.h>
 #include <linux/regmap.h>
 #include <linux/regulator/consumer.h>
 #include <linux/resource.h>
@@ -297,8 +298,15 @@ static int imx6q_pcie_abort_handler(unsigned long addr,
 		unsigned int fsr, struct pt_regs *regs)
 {
 	unsigned long pc = instruction_pointer(regs);
-	unsigned long instr = *(unsigned long *)pc;
-	int reg = (instr >> 12) & 15;
+	unsigned long instr;
+	int reg;
+
+	/* if the abort from user-space, just return and report it */
+	if (user_mode(regs))
+		return 1;
+
+	instr = *(unsigned long *)pc;
+	reg = (instr >> 12) & 15;
 
 	/*
 	 * If the instruction being executed was a read,
-- 
2.25.1