linux-kernel - Re: [PATCH v7 05/19] iov_iter: Introduce fault_in_iov_iter

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Date:   Sun, 29 Aug 2021 19:46:04 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     "Luck, Tony" <tony.luck@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andreas Gruenbacher <agruenba@...hat.com>,
        Christoph Hellwig <hch@...radead.org>,
        "Darrick J. Wong" <djwong@...nel.org>, Jan Kara <jack@...e.cz>,
        Matthew Wilcox <willy@...radead.org>,
        cluster-devel <cluster-devel@...hat.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        ocfs2-devel@....oracle.com, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org
Subject: Re: [PATCH v7 05/19] iov_iter: Introduce fault_in_iov_iter_writeable

On Sun, Aug 29, 2021 at 08:44:04PM +0200, Thomas Gleixner wrote:
> On Sat, Aug 28 2021 at 22:51, Al Viro wrote:
> > @@ -345,7 +346,7 @@ static inline int xsave_to_user_sigframe(struct xregs_state __user *buf)
> >  	 */
> >  	err = __clear_user(&buf->header, sizeof(buf->header));
> >  	if (unlikely(err))
> > -		return -EFAULT;
> > +		return -X86_TRAP_PF;
> 
> This clear_user can be lifted into copy_fpstate_to_sigframe(). Something
> like the below.

Hmm...  This mixing of -X86_TRAP_... with -E... looks like it's asking for
trouble in general.  Might be worth making e.g. fpu__restore_sig() (and
its callers) return bool, seeing that we only check for 0/non-zero in
there.