netdev - RE: [PATCH net 0/3] Fix for BPF devmap percpu allocation splat

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Date:   Tue, 17 Oct 2017 15:03:07 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Daniel Borkmann' <daniel@...earbox.net>,
        "davem@...emloft.net" <davem@...emloft.net>
CC:     "tj@...nel.org" <tj@...nel.org>, "ast@...nel.org" <ast@...nel.org>,
        "john.fastabend@...il.com" <john.fastabend@...il.com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "richard@....at" <richard@....at>,
        "sp3485@...umbia.edu" <sp3485@...umbia.edu>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH net 0/3] Fix for BPF devmap percpu allocation splat

From: Daniel Borkmann
> Sent: 17 October 2017 15:56
> 
> The set fixes a splat in devmap percpu allocation when we alloc
> the flush bitmap. Patch 1 is a prerequisite for the fix in patch 2,
> patch 1 is rather small, so if this could be routed via -net, for
> example, with Tejun's Ack that would be good. Patch 3 gets rid of
> remaining PCPU_MIN_UNIT_SIZE checks, which are percpu allocator
> internals and should not be used.

Does it make sense to allow the user program to try to allocate ever
smaller very large maps until it finds one that succeeds - thus
using up all the percpu space?

Or is this a 'root only' 'shoot self in foot' job?

	David