linux-kernel - Re: [PATCH] userfaultfd: release page in error path to avoid BUG

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Message-ID: <20210428212430.GA6462@xz-x1>
Date:   Wed, 28 Apr 2021 17:24:30 -0400
From:   Peter Xu <peterx@...hat.com>
To:     Hugh Dickins <hughd@...gle.com>
Cc:     Axel Rasmussen <axelrasmussen@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Lokesh Gidra <lokeshgidra@...gle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] userfaultfd: release page in error path to avoid BUG_ON

On Wed, Apr 28, 2021 at 02:03:05PM -0700, Hugh Dickins wrote:

[...]

> > > +			put_page(*pagep);
> > > +			*pagep = NULL;
> > > +		}
> > >  		goto out;
> > 
> > All "goto out" in this functions looks weird as it returns directly... so if
> > you're touching this after all, I suggest we do "return -ENOMEM" directly and
> > drop the "ret = -ENOMEM".
> 
> No strong feeling either way from me on that: whichever looks best
> to you.  But I suspect the "ret = -ENOMEM" cannot be dropped,
> because it's relied on further down too?

Ah sorry I just noticed Axel didn't really touch that line.. :) So yeah please
also feel free to keep it as is.

If to drop it, "ret = -ENOMEM" can go as well, I think.. since all later errors
should always reset variable "ret".

Thanks,

-- 
Peter Xu