linux-kernel - Re: [PATCH] MIPS: fw: Gracefully handle unknown firmware protocols

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Message-Id: <7f0602dc-8a47-46cb-a12f-09afc082b48f@app.fastmail.com>
Date: Sun, 25 Aug 2024 13:50:20 +0100
From: "Jiaxun Yang" <jiaxun.yang@...goat.com>
To: Bjørn Mork <bjorn@...k.no>,
 "Thomas Bogendoerfer" <tsbogend@...ha.franken.de>
Cc: "Steven J . Hill" <Steven.Hill@...tec.com>,
 "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
 linux-kernel@...r.kernel.org,
 "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH] MIPS: fw: Gracefully handle unknown firmware protocols



在2024年8月24日八月 下午3:41，Bjørn Mork写道：
> Boards based on the same SoC family can use different boot loaders.
> These may pass numeric arguments which we erroneously interpret as
> command line or environment pointers. Such errors will cause boot
> to halt at an early stage since commit 056a68cea01e ("mips: allow
> firmware to pass RNG seed to kernel").
>
> One known example of this issue is a HPE switch using a BootWare
> boot loader.  It was found to pass these arguments to the kernel:
>
>   0x00020000 0x00060000 0xfffdffff 0x0000416c
>
> We can avoid hanging by validating that both passed pointers are in
> KSEG1 as expected.

Hi Bjorn,

This is actually breaking 64 bit systems passing fw_args in XKPHYS or KSEG0.

Maybe something like:

static inline bool valid_fw_arg(unsigned long arg)
{
#ifdef CONFIG_64BIT
	if (arg >= XKPHYS && arg < XKSEG)
		return TRUE;
#endif
	return arg >= CKSEG0 && arg < CKSSEG;
}

Will be more robust.

Thanks
- Jiaxun

>
> Cc: stable@...r.kernel.org
> Fixes: 14aecdd41921 ("MIPS: FW: Add environment variable processing.")
> Signed-off-by: Bjørn Mork <bjorn@...k.no>
> ---
>  arch/mips/fw/lib/cmdline.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/mips/fw/lib/cmdline.c b/arch/mips/fw/lib/cmdline.c
> index 892765b742bb..51238c4f9455 100644
> --- a/arch/mips/fw/lib/cmdline.c
> +++ b/arch/mips/fw/lib/cmdline.c
> @@ -22,7 +22,7 @@ void __init fw_init_cmdline(void)
>  	int i;
> 
>  	/* Validate command line parameters. */
> -	if ((fw_arg0 >= CKSEG0) || (fw_arg1 < CKSEG0)) {
> +	if (fw_arg0 >= CKSEG0 || fw_arg1 < CKSEG0 || fw_arg1 >= CKSEG2) {
>  		fw_argc = 0;
>  		_fw_argv = NULL;
>  	} else {
> @@ -31,7 +31,7 @@ void __init fw_init_cmdline(void)
>  	}
> 
>  	/* Validate environment pointer. */
> -	if (fw_arg2 < CKSEG0)
> +	if (fw_arg2 < CKSEG0 || fw_arg2 >= CKSEG2)
>  		_fw_envp = NULL;
>  	else
>  		_fw_envp = (int *)fw_arg2;
> -- 
> 2.39.2

-- 
- Jiaxun