On Tuesday, January 27, 2015 8:59 AM, Ian Abbott wrote:
> On 27/01/15 15:50, Ian Abbott wrote:
>> `do_cmd_ioctl()` in "comedi_fops.c" handles the `COMEDI_CMD` ioctl.
>> This returns `-EAGAIN` if it has copied a modified `struct comedi_cmd`
>> back to user-space. (This occurs when the low-level Comedi driver's
>> `do_cmdtest()` handler returns non-zero to indicate a problem with the
>> contents of the `struct comedi_cmd`, or when the `struct comedi_cmd` has
>> the `CMDF_BOGUS` flag set.)
>>
>> `compat_cmd()` in "comedi_compat32.c" handles the 32-bit compatible
>> version of the `COMEDI_CMD` ioctl. Currently, it never copies a 32-bit
>> compatible version of `struct comedi_cmd` back to user-space, which is
>> at odds with the way the regular `COMEDI_CMD` ioctl is handled. To fix
>> it, change `compat_cmd()` to copy a 32-bit compatible version of the
>> `struct comedi_cmd` back to user-space when the main ioctl handler
>> returns `-EAGAIN`.
>>
>> Signed-off-by: Ian Abbott <abbotti@xxxxxxxxx>
>> Cc: <stable@xxxxxxxxxxxxxxx>
>> ---
>> drivers/staging/comedi/comedi_compat32.c | 13 +++++++++++--
>> 1 file changed, 11 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/staging/comedi/comedi_compat32.c b/drivers/staging/comedi/comedi_compat32.c
>> index 5a4c74f..2440c60 100644
>> --- a/drivers/staging/comedi/comedi_compat32.c
>> +++ b/drivers/staging/comedi/comedi_compat32.c
>> @@ -262,7 +262,8 @@ static int compat_cmd(struct file *file, unsigned long arg)
>> {
>> struct comedi_cmd __user *cmd;
>> struct comedi32_cmd_struct __user *cmd32;
>> - int rc;
>> + long rc;
>> + int err;
>
> Gah! That change in type of the 'rc' variable resulted from me changing
> the order of the patches in the series. It still works, but looks a bit
> out of place. Should I post an updated version without this niggle?
Please fix it. I does look strange. Actually, the last patch looks strange.
The "normal" return type in the kernel is an 'int'. As you mention in the
commit message: "The `unlocked_ioctl` and `compat_ioctl` file operations
are both defined to return a `long` (I don't know why)." It seems cleaner
to just have all the static functions return an int and just have
comedi_compat_ioctl() return the long value. Maybe just add a comment
why...
My 2 cents...
Regards,
Hartley
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