linux-kernel - Re: [PATCH 1/1] module: fix sprintf format specifier in param_get

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Date:	Wed, 07 Aug 2013 16:13:57 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Christoph Jaeger <christophjaeger@...ux.com>
Cc:	linux-kernel@...r.kernel.org,
	Dmitry Tarnyagin <dmitry.tarnyagin@...kless.no>,
	Jon Mason <jon.mason@...el.com>, tech.support@...lex.com,
	"David Woodhouse" <dwmw2@...radead.org>,
	Michal Nazarewicz <mina86@...a86.com>
Subject: Re: [PATCH 1/1] module: fix sprintf format specifier in param_get_byte()

Christoph Jaeger <christophjaeger@...ux.com> writes:
> In param_get_byte(), to which the macro STANDARD_PARAM_DEF(byte, ...) expands,
> "%c" is used to print an unsigned char. So it gets printed as a character what
> is not intended here. Use "%hhu" instead.
>
> Signed-off-by: Christoph Jaeger <christophjaeger@...ux.com>

Nice patch.  Unfortunately, there are several users of this already:

drivers/net/wireless/cw1200/main.c:50:module_param_array_named(macaddr, cw1200_mac_template, byte, NULL, S_IRUGO);
drivers/ntb/ntb_transport.c:68:module_param(max_num_clients, byte, 0644);
drivers/scsi/lpfc/lpfc_attr.c:4207:module_param(lpfc_prot_guard, byte, S_IRUGO);
drivers/usb/atm/speedtch.c:117:module_param(ModemMode, byte, S_IRUGO | S_IWUSR);
drivers/usb/atm/speedtch.c:121:module_param_array(ModemOption, byte, &num_ModemOption, S_IRUGO);
drivers/usb/gadget/g_ffs.c:95:module_param_named(bDeviceClass,    gfs_dev_desc.bDeviceClass,    byte,   0644);
drivers/usb/gadget/g_ffs.c:97:module_param_named(bDeviceSubClass, gfs_dev_desc.bDeviceSubClass, byte,   0644);
drivers/usb/gadget/g_ffs.c:99:module_param_named(bDeviceProtocol, gfs_dev_desc.bDeviceProtocol, byte,   0644);

I have CC'd all the authors, to see if changing the results of reading
/sys/module/<modname>/parameters/<xxx> from a literal char to a number
will harm them.

Thanks,
Rusty.

> ---
>  kernel/params.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/params.c b/kernel/params.c
> index 440e65d..59f7ac7 100644
> --- a/kernel/params.c
> +++ b/kernel/params.c
> @@ -252,7 +252,7 @@ int parse_args(const char *doing,
>  	EXPORT_SYMBOL(param_ops_##name)
>  
>  
> -STANDARD_PARAM_DEF(byte, unsigned char, "%c", unsigned long, strict_strtoul);
> +STANDARD_PARAM_DEF(byte, unsigned char, "%hhu", unsigned long, strict_strtoul);
>  STANDARD_PARAM_DEF(short, short, "%hi", long, strict_strtol);
>  STANDARD_PARAM_DEF(ushort, unsigned short, "%hu", unsigned long, strict_strtoul);
>  STANDARD_PARAM_DEF(int, int, "%i", long, strict_strtol);
> -- 
> 1.8.3.1
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