netdev - Re: [PATCH net] net: deal with integer overflows in kmalloc

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Message-ID: <CANn89iKL9-3RTBhtyg5gxOLfXZVyJoCK0A_K9ui5Ew-KdNtFhw@mail.gmail.com>
Date: Tue, 5 Sep 2023 14:34:11 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: David Laight <David.Laight@...lab.com>
Cc: Kyle Zeng <zengyhkyle@...il.com>, "David S . Miller" <davem@...emloft.net>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>, "eric.dumazet@...il.com" <eric.dumazet@...il.com>, 
	syzbot <syzkaller@...glegroups.com>, Kees Cook <keescook@...omium.org>, 
	Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [PATCH net] net: deal with integer overflows in kmalloc_reserve()

On Tue, Sep 5, 2023 at 2:27 PM Eric Dumazet <edumazet@...gle.com> wrote:
>
> On Tue, Sep 5, 2023 at 10:36 AM David Laight <David.Laight@...lab.com> wrote:
> >
> > From: Eric Dumazet
> > > Sent: 05 September 2023 04:42
> > ...
> > > Again, I do not want this patch, I want to fix the root cause(s).
> > >
> > > It makes no sense to allow dev->mtu to be as big as 0x7fffffff and
> > > ultimately allow size to be bigger than 0x80000000
> >
> > kmem_alloc_reserve() also needs fixing.
>
> Yes, this is what I said. Please provide a patch ?

Oops, I thought you were speaking about kmalloc_size_roundup()

kmalloc_reserve() is fine, all overflows must be taken care of before
reaching it.