linux-kernel - Re: [PATCH 2/2] vmalloc: reject vmap with VM_FLUSH_RESET

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Date:   Fri, 23 Dec 2022 14:10:32 +0000
From:   Lorenzo Stoakes <lstoakes@...il.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Uladzislau Rezki <urezki@...il.com>,
        linux-arm-msm@...r.kernel.org, linux-remoteproc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        iommu@...ts.linux.dev
Subject: Re: [PATCH 2/2] vmalloc: reject vmap with VM_FLUSH_RESET_PERMS

On Fri, Dec 23, 2022 at 03:03:12PM +0100, Christoph Hellwig wrote:
> On Fri, Dec 23, 2022 at 10:24:25AM +0000, Lorenzo Stoakes wrote:
> > Might it be worth adding a specific vmap mask that explicitly indicates what
> > flags are permissible on vmap()? Then this could become e.g.:-
> >
> > 	if (WARN_ON_ONCE(flags & ~VM_VMAP_PERMITTED_MASK))
> > 		return NULL;
> >
> > And would be self-documenting as to why we are disallowing flags (i.e. they are
> > not part of the permitted vmap mask).
>
> That's probably a good idea.  It might need some time to audit
> for use of all the flags, though.

Perhaps leave that for a later patch (I could take a look as well), but in the
meantime might be worth adding a quick comment here indicating why the flag is
prohibited?