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

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Message-ID: <Yapx9+fakH6GYpcO@google.com>
Date:   Fri, 3 Dec 2021 19:37:27 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Bixuan Cui <cuibixuan@...ux.alibaba.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
        leon@...nel.org, w@....eu, keescook@...omium.org,
        bpf@...r.kernel.org, netdev@...r.kernel.org,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jakub Kicinski <kuba@...nel.org>, kvm@...r.kernel.org,
        netfilter-devel@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH -next] mm: delete oversized WARN_ON() in kvmalloc() calls

+Paolo, I'm pretty sure he's still not subscribed to the KVM mailing list :-)

On Wed, Dec 01, 2021, Andrew Morton wrote:
> On Thu, 2 Dec 2021 12:05:15 +0800 Bixuan Cui <cuibixuan@...ux.alibaba.com> wrote:
> 
> > 
> > 在 2021/12/2 上午11:26, Andrew Morton 写道:
> > >> Delete the WARN_ON() and return NULL directly for oversized parameter
> > >> in kvmalloc() calls.
> > >> Also add unlikely().
> > >>
> > >> Fixes: 7661809d493b ("mm: don't allow oversized kvmalloc() calls")
> > >> Signed-off-by: Bixuan Cui<cuibixuan@...ux.alibaba.com>
> > >> ---
> > >> There are a lot of oversize warnings and patches about kvmalloc() calls
> > >> recently. Maybe these warnings are not very necessary.
> > > Or maybe they are.  Please let's take a look at these warnings, one at
> > > a time.  If a large number of them are bogus then sure, let's disable
> > > the runtime test.  But perhaps it's the case that calling code has
> > > genuine issues and should be repaired.
> > Such as：
> 
> Thanks, that's helpful.
> 
> Let's bring all these to the attention of the relevant developers.
> 
> If the consensus is "the code's fine, the warning is bogus" then let's
> consider retiring the warning.
> 
> If the consensus is otherwise then hopefully they will fix their stuff!
> 
> 
> 
> > https://syzkaller.appspot.com/bug?id=24452f89446639c901ac07379ccc702808471e8e
> 
> (cc bpf@...r.kernel.org)
> 
> > https://syzkaller.appspot.com/bug?id=f7c5a86e747f9b7ce333e7295875cd4ede2c7a0d
> 
> (cc netdev@...r.kernel.org, maintainers)
> 
> > https://syzkaller.appspot.com/bug?id=8f306f3db150657a1f6bbe1927467084531602c7
> 
> (cc kvm@...r.kernel.org)

Paolo posted patches to resolve the KVM issues, but I don't think they ever got
applied.

https://lore.kernel.org/all/20211016064302.165220-1-pbonzini@redhat.com/
https://lore.kernel.org/all/20211015165519.135670-1-pbonzini@redhat.com/