Quoting James Morris ([EMAIL PROTECTED]):
> On Mon, 6 Aug 2007, Serge E. Hallyn wrote:
>
> > + err = security_inode_killpriv(out->f_path.dentry, LSM_NEED_LOCK);
> > + if (err)
> > + return err;
> > +
> > err = should_remove_suid(out->f_path.dentry);
> > if (unlikely(err)) {
> > mutex_lock(&inode->i_mutex);
>
> It seems hackish to pass a needlock arg to an API, and that that we'll end
> up with some conceptually similar call-outs for both caps and setuid.
>
> How about encapsulating this stuff so that there's something like:
>
>
> err = should_remove_privs();
> if (err)
> remove_privs();
>
> with
>
> void remove_privs()
> {
> mutex_lock();
> __remove_privs();
> mutex_unlock();
> }
>
> and then __remove_privs() handles the logic for all file privileges,
> including at this stage suid and the LSM call for file caps ?
The problem is that the suid bit is not removed in all cases
when the file caps need to be removed. In particular, if
capable(CAP_FSETID), then the suid bit is retained.
I suppose we could change those semantics, but then we'd the code still
doesn't flow quite right for what you suggest - should_remove_suid()
just checks whether the suid bit is set (and the process is
!capable(CAP_FSETID),
not whether a change has happened requiring suid change. That is
already assumed to be the case.
If your main objection is to the LSM_NEED_LOCK argument, we could of
course just grab the mutex around security_inode_killpriv(out->f_path.dentry)
in fs/splice.c:generic_file_splice_write().
And I suppose we can in fact get rid of ATTR_KILL_PRIV. I had just
put it there to split up the code a bit to make it clearer - which I
do think it does.
Shall I resend without the LSM_NEED_LOCK, or do you still want a more
fundamental change?
thanks,
-serge
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