[RFC PATCH] PCI: imx6: Handle the abort from user-space

[Hongxing Zhu]

> -----Original Message-----
> From: Francesco Dolcini <francesco.dolcini at toradex.com>
> Sent: 2022Äê1ÔÂ28ÈÕ 16:29
> To: Hongxing Zhu <hongxing.zhu at nxp.com>; Lucas Stach
> <l.stach at pengutronix.de>; Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>; Rob
> Herring <robh at kernel.org>; Krzysztof Wilczy¨½ski <kw at linux.com>; Sascha
> Hauer <s.hauer at pengutronix.de>; Pengutronix Kernel Team
> <kernel at pengutronix.de>; Fabio Estevam <festevam at gmail.com>;
> dl-linux-imx <linux-imx at nxp.com>; Jason Liu <jason.hui.liu at nxp.com>
> Cc: linux-pci at vger.kernel.org; linux-arm-kernel at lists.infradead.org;
> linux-kernel at vger.kernel.org; Bjorn Helgaas <bhelgaas at google.com>; Shawn
> Guo <shawnguo at kernel.org>; Francesco Dolcini
> <francesco.dolcini at toradex.com>
> Subject: [RFC PATCH] PCI: imx6: Handle the abort from user-space
> 
> From: Jason Liu <jason.hui.liu at nxp.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.
> 
> Signed-off-by: Jason Liu <jason.hui.liu at nxp.com>
> Reviewed-by: Richard Zhu <hongxing.zhu at nxp.com>
> Signed-off-by: Francesco Dolcini <francesco.dolcini at toradex.com>
> ---
> We have this patch from NXP downstream kernel [1] in our kernel branch [2]
> since a long time, to me it would make sense to upstream it. Any concern?
> 
> [1]
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fsource.
> codeaurora.org%2Fexternal%2Fimxsupport%2Flinux-imx%2Fcommit%2F%3Fid
> %3D62dfb2fb953463dd1b6710567c9e174672a98f24&data=04%7C01%7
> Chongxing.zhu%40nxp.com%7Ccbe193ab4c3e4ad11bcb08d9e2384a1f%7C68
> 6ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637789553659549198%7
> CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBT
> iI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=Mwhx8DFF7EDJdpqTsHT
> %2BBAGzhQadDOqcgJnVjeoi1yk%3D&reserved=0
> [2]
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.tora
> dex.com%2Fcgit%2Flinux-toradex.git%2Fcommit%2F%3Fid%3D2b42547cf659f
> 979be2defdff6a99f921b33d0f1&data=04%7C01%7Chongxing.zhu%40nx
> p.com%7Ccbe193ab4c3e4ad11bcb08d9e2384a1f%7C686ea1d3bc2b4c6fa92c
> d99c5c301635%7C0%7C0%7C637789553659549198%7CUnknown%7CTWFp
> bGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI
> 6Mn0%3D%7C3000&sdata=QEW1frh8WacCzniWo4ng1cy3Z1UZ9uMRFw
> GBKuIh7zE%3D&reserved=0
> ---
>  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..6b178a29e253 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -27,6 +27,7 @@
>  #include <linux/resource.h>
>  #include <linux/signal.h>
>  #include <linux/types.h>
> +#include <linux/uaccess.h>

[Richard Zhu] Thanks for your kindly help.
This header include is not required actually, please remove it.
Best Regards
Richard

>  #include <linux/interrupt.h>
>  #include <linux/reset.h>
>  #include <linux/phy/phy.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