[PATCH 1/1] module: fix sprintf format specifier in param_get_byte()

[Christoph Jaeger]

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 <christo...@linux.com>
---
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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[Joe Perches]

On Tue, 2013-08-06 at 23:12 +0200, Christoph Jaeger wrote:
> 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 <christo...@linux.com>
> ---
> 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);

I don't see the point of using "%hh[ui]" and "%h[ui]".
These are promoted to int/unsigned int for the sprintf anyway.
I'd just use %d and %u instead.

[Rusty Russell]

Christoph Jaeger <christo...@linux.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 <christo...@linux.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.

[Michal Nazarewicz]

On Wed, Aug 07 2013, Rusty Russell wrote:
> Christoph Jaeger <christo...@linux.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 <christo...@linux.com>

Acked-by: Michal Nazarewicz <min...@mina86.com>

for g_ffs.c:

> 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 don't think it breaks anything for g_ffs since those properties are
most likely write-only and I don't expect many people reading them.

>> ---
>> 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);

Actually, are those “h” specifiers even necessary? I'm fairly certain
that “%u” for byte, “%i” for short, and “%u” for ushort would work just
fine since the argument gets promoted to (unsigned) int anyway and
indeed vsnprintf reads an int for all those types.

>> STANDARD_PARAM_DEF(int, int, "%i", long, strict_strtol);

--

Best regards, _ _
.o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o
..o | Computer Science, Michał “mina86” Nazarewicz (o o)
ooo +----<email/xmpp: m...@google.com>--------------ooO--(_)--Ooo--

[Jon Mason]

On Wed, Aug 07, 2013 at 04:13:57PM +0930, Rusty Russell wrote:
> Christoph Jaeger <christo...@linux.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 <christo...@linux.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);

This shouldn't affect NTB negatively.

Acked-by: Jon Mason <jon....@intel.com>