linux-kernel - Re: [PATCH v2 1/2] pci: imx6: avoid dereferencing program counter from user mode

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Message-ID: <20190208121341.GD13009@e107981-ln.cambridge.arm.com>
Date:   Fri, 8 Feb 2019 12:13:41 +0000
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Stefan Agner <stefan@...er.ch>
Cc:     hongxing.zhu@....com, l.stach@...gutronix.de, robin.murphy@....com,
        tpiepho@...inj.com, linux@...linux.org.uk, leonard.crestez@....com,
        andrew.smirnov@...il.com, festevam@...il.com, bhelgaas@...gle.com,
        linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] pci: imx6: avoid dereferencing program counter
 from user mode

On Tue, Dec 04, 2018 at 02:27:32PM +0100, Stefan Agner wrote:
> The custom fault handler is currently only meant to handle kernel
> mode bus faults. Exit in case the abort happened in user mode.
> 
> Signed-off-by: Stefan Agner <stefan@...er.ch>
> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)

If this series is still aimed at mainline I need Lucas' ACK to
merge it.

Lorenzo

> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index 69f86234f7c0..54a29e441303 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -270,8 +270,14 @@ 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 (user_mode(regs))
> +		return 1;
> +
> +	instr = *(unsigned long *)pc;
> +	reg = (instr >> 12) & 15;
>  
>  	/*
>  	 * If the instruction being executed was a read,
> -- 
> 2.19.1
>