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Date: Sun, 26 Apr 2015 16:09:10 -0400 (EDT)
From: David Miller <davem@...emloft.net>
To: eric.dumazet@...il.com
Cc: netdev@...r.kernel.org, tom@...bertland.com, ben@...adent.org.uk
Subject: Re: [PATCH net] net: rfs: fix crash in get_rps_cpus()
From: Eric Dumazet <eric.dumazet@...il.com>
Date: Sat, 25 Apr 2015 09:35:24 -0700
> From: Eric Dumazet <edumazet@...gle.com>
>
> Commit 567e4b79731c ("net: rfs: add hash collision detection") had one
> mistake :
>
> RPS_NO_CPU is no longer the marker for invalid cpu in set_rps_cpu()
> and get_rps_cpu(), as @next_cpu was the result of an AND with
> rps_cpu_mask
>
> This bug showed up on a host with 72 cpus :
> next_cpu was 0x7f, and the code was trying to access percpu data of an
> non existent cpu.
>
> In a follow up patch, we might get rid of compares against nr_cpu_ids,
> if we init the tables with 0. This is silly to test for a very unlikely
> condition that exists only shortly after table initialization, as
> we got rid of rps_reset_sock_flow() and similar functions that were
> writing this RPS_NO_CPU magic value at flow dismantle : When table is
> old enough, it never contains this value anymore.
>
> Fixes: 567e4b79731c ("net: rfs: add hash collision detection")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Tom Herbert <tom@...bertland.com>
> Cc: Ben Hutchings <ben@...adent.org.uk>
Applied and queued up for 4.0-stable, thanks Eric.
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