On Thu, 2007-03-01 at 17:46 +0800, Ian jonhson wrote:
> On 2/7/07, Casey Schaufler <[EMAIL PROTECTED]> wrote:
> >
> > --- Ian jonhson <[EMAIL PROTECTED]> wrote:
> >
> >
> > > static int my_setprocattr(struct task_struct *p,
> > > char *name, void
> > > *value, size_t size)
> > > {
> > > my_struct sl;
> > > my_struct* ts;
> > >
> > > if(current != p)
> > > return -EACCES;
> > >
> > > if(!size)
> > > return -ERANGE;
> > >
> > > if(!strcmp(name, "current"))
> > > {
> > > if (copy_from_user(&sl, value, sizeof(my_struct)))
> > > {
> > > return -EFAULT;
> > > }
> >
> >
> > "value" is a kernel address, not a user address.
> > You can replace this with:
> >
> > memcpy(&sl, value, sizeof(my_struct));
> >
> > >
> > > ts = p->security;
> > > if(ts)
> > > {
> > > ts->v1 = sl.v1;
> > > ts->v2 = sl.v2;
> > >
> > > }
> > > else
> > > {
> > > ts->v1 = UNDEFINE_V1;
> > > ts->v2 = UNDEFINE_V2;
> > > }
> >
> > If ts is NULL this will not work, you know.
> >
> > >
> > >
> > > return 0;
> > > }
> > >
> > > return size;
> > > }
> > >
> > > After compiling the module and insmod it, I run my
> > > setselfattr codes
> > > mentioned last mail and got another error message:
> > >
> > > write failed due to: Bad address
> > >
> > > Maybe, there are indeed something wrong with my
> > > hook.
> >
> > The change from copy_from_user to memcpy will
> > take care of today's problem, but you still need to
> > be carefull about your pointers. If ts is NULL
> > the code presented will crash.
> >
>
> Ok, change to memcpy(). However, no matter what the function is memcpy
> or copy_from_user, I all get the error message:
>
> write failed due to: Bad address
>
> what is the meaning of "Bad address"? Error in kernel address or user address?
>
> I have traced the error several days, but nothing can be done to help me.
"Bad address" == EFAULT, i.e. the buf pointer passed to write() is
outside your program's address space.
As usual, it is harder to help you without seeing your code than it
would be if you showed it...
--
Stephen Smalley
National Security Agency
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