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

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Message-ID: <1549904165.2546.14.camel@pengutronix.de>
Date:   Mon, 11 Feb 2019 17:56:05 +0100
From:   Lucas Stach <l.stach@...gutronix.de>
To:     Stefan Agner <stefan@...er.ch>, hongxing.zhu@....com
Cc:     robin.murphy@....com, tpiepho@...inj.com, linux@...linux.org.uk,
        leonard.crestez@....com, andrew.smirnov@...il.com,
        festevam@...il.com, lorenzo.pieralisi@....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

Am Dienstag, den 04.12.2018, 14:27 +0100 schrieb Stefan Agner:
> 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>

Reviewed-by: Lucas Stach <l.stach@...gutronix.de>

> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> 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,