linux-kernel - Re: [PATCH -next] mm: delete oversized WARN

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Date:   Thu, 2 Dec 2021 14:03:43 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Leon Romanovsky <leon@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Bixuan Cui <cuibixuan@...ux.alibaba.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
        w@....eu
Subject: Re: [PATCH -next] mm: delete oversized WARN_ON() in kvmalloc()
 calls

On Thu, 2 Dec 2021 13:23:13 -0800 Kees Cook <keescook@...omium.org> wrote:

> > > I think we have two cases:
> > > 
> > > - limiting kvmalloc allocations to INT_MAX
> > > - issuing a WARN when that limit is exceeded
> > > 
> > > The argument for the having the WARN is "that amount should never be
> > > allocated so we want to find the pathological callers".
> > > 
> > > But if the actual issue is that >INT_MAX is _acceptable_, then we have
> > > to do away with the entire check, not just the WARN.
> > 
> > First we need to get rid from WARN_ON(), which is completely safe thing to do.
> > 
> > Removal of the check can be done in second step as it will require audit
> > of whole kvmalloc* path.
> 
> If those are legit sizes, I'm fine with dropping the WARN. (But I still
> think if they're legit sizes, we must also drop the INT_MAX limit.)

Can we suppress the WARN if the caller passed __GFP_NOWARN?