Re: [patch v2] fcntl: return -EFAULT if copy_to_user fails

[Takuya Yoshikawa]

(2010/06/03 22:10), Nick Piggin wrote:
> On Thu, Jun 03, 2010 at 02:38:03PM +0200, Eric Dumazet wrote:
> > Le jeudi 03 juin 2010 à 21:16 +0900, Takuya Yoshikawa a écrit :
> > > (2010/06/03 20:59), Jens Axboe wrote:
> > > > On 2010-06-03 12:35, Dan Carpenter wrote:
> > > > > copy_to_user() returns the number of bytes remaining, but we want to
> > > > > return -EFAULT.
> > > > > 	ret = fcntl(fd, F_SETOWN_EX, NULL);
> > > > > With the original code ret would be 8 here.
> > > > >
> > > > > V2: Takuya Yoshikawa pointed out a similar issue in f_getown_ex()
> > > >
> > > > Pretty basic bug, how long has this been there?
> > >
> > > IIUC, from the beginning, when these were introduced.
> >
> > Maybe copy_to_user() was changed sometime to return a partial count
> > instead of EFAULT ?
>
> I think it's been like that since first introduced. Some functions
> do need to know in order to do partial copies.
>
>
> > I do think we should have a set of helper functions, instead of
> > spreading special EFAULT cases in one housand places...
> >
> > This is really ugly.
> >
> > static inline int sec_copy_to_user(arg1, arg2, arg3)
> > {
> > 	int res = copy_to_user(arg1, arg2, arg3);
> >
> > 	return (res>  0) ? -EFAULT : res;
> > }
>
> It would be unfortunate if it adds more confusion. I'd prefer to have
> a sufficiently different name. memcpy_to_user/memcpy_from_user
> perhaps?

Then, and memclear_user() ?

>

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