linux-kernel - Re: [PATCH v3] 9p: client_create/destroy: only call trans

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Date:   Thu, 29 Sep 2022 16:24:10 +0900
From:   Dominique Martinet <asmadeus@...ewreck.org>
To:     Leon Romanovsky <leon@...nel.org>
Cc:     v9fs-developer@...ts.sourceforge.net, linux_oss@...debyte.com,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        syzbot+67d13108d855f451cafc@...kaller.appspotmail.com
Subject: Re: [PATCH v3] 9p: client_create/destroy: only call trans_mod->close
 after create

Leon Romanovsky wrote on Thu, Sep 29, 2022 at 08:54:10AM +0300:
> > +	// ensure clnt->trans is initialized to call close() on destroy
> > +	// if and only if create succeeded
> > +	if (err < 0) {
> > +		clnt->trans = ERR_PTR(err);
> >  		goto out;
> > +	}
> > +	if (IS_ERR(clnt->trans))
> > +		clnt->trans = NULL;
> >  
> >  	if (clnt->msize > clnt->trans_mod->maxsize) {
> >  		clnt->msize = clnt->trans_mod->maxsize;
> > @@ -1036,7 +1043,7 @@ void p9_client_destroy(struct p9_client *clnt)
> >  
> >  	p9_debug(P9_DEBUG_MUX, "clnt %p\n", clnt);
> >  
> > -	if (clnt->trans_mod)
> > +	if (clnt->trans_mod && !IS_ERR(clnt->trans))
> 
> It is completely no-go to rely on internal value inside of structure after
> failure in ->create() callback.

We're overriding the value after ->create(), in both cases that might
pose problem (success without setting trans/failure); I can't see how
that would possibly fail.

But as you've seen in the other commit I am in no shape to write any
decent code and consider the implications of what I'm changing in this
untangled mess, so you know what: I'll just leave this broken.

Please send me a patch if you care, I'm done here.
-- 
Dominique