[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20190923151519.GE2369@hirez.programming.kicks-ass.net>
Date: Mon, 23 Sep 2019 17:15:19 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Yunsheng Lin <linyunsheng@...wei.com>
Cc: catalin.marinas@....com, will@...nel.org, mingo@...hat.com,
bp@...en8.de, rth@...ddle.net, ink@...assic.park.msu.ru,
mattst88@...il.com, benh@...nel.crashing.org, paulus@...ba.org,
mpe@...erman.id.au, heiko.carstens@...ibm.com, gor@...ux.ibm.com,
borntraeger@...ibm.com, ysato@...rs.sourceforge.jp,
dalias@...c.org, davem@...emloft.net, ralf@...ux-mips.org,
paul.burton@...s.com, jhogan@...nel.org, jiaxun.yang@...goat.com,
chenhc@...ote.com, akpm@...ux-foundation.org, rppt@...ux.ibm.com,
anshuman.khandual@....com, tglx@...utronix.de, cai@....pw,
robin.murphy@....com, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org, hpa@...or.com, x86@...nel.org,
dave.hansen@...ux.intel.com, luto@...nel.org, len.brown@...el.com,
axboe@...nel.dk, dledford@...hat.com, jeffrey.t.kirsher@...el.com,
linux-alpha@...r.kernel.org, naveen.n.rao@...ux.vnet.ibm.com,
mwb@...ux.vnet.ibm.com, linuxppc-dev@...ts.ozlabs.org,
linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
sparclinux@...r.kernel.org, tbogendoerfer@...e.de,
linux-mips@...r.kernel.org, rafael@...nel.org, mhocko@...nel.org,
gregkh@...uxfoundation.org
Subject: Re: [PATCH v6] numa: make node_to_cpumask_map() NUMA_NO_NODE aware
On Tue, Sep 17, 2019 at 08:48:54PM +0800, Yunsheng Lin wrote:
> When passing the return value of dev_to_node() to cpumask_of_node()
> without checking if the device's node id is NUMA_NO_NODE, there is
> global-out-of-bounds detected by KASAN.
>
> From the discussion [1], NUMA_NO_NODE really means no node affinity,
> which also means all cpus should be usable. So the cpumask_of_node()
> should always return all cpus online when user passes the node id as
> NUMA_NO_NODE, just like similar semantic that page allocator handles
> NUMA_NO_NODE.
>
> But we cannot really copy the page allocator logic. Simply because the
> page allocator doesn't enforce the near node affinity. It just picks it
> up as a preferred node but then it is free to fallback to any other numa
> node. This is not the case here and node_to_cpumask_map will only restrict
> to the particular node's cpus which would have really non deterministic
> behavior depending on where the code is executed. So in fact we really
> want to return cpu_online_mask for NUMA_NO_NODE.
>
> Also there is a debugging version of node_to_cpumask_map() for x86 and
> arm64, which is only used when CONFIG_DEBUG_PER_CPU_MAPS is defined, this
> patch changes it to handle NUMA_NO_NODE as normal node_to_cpumask_map().
>
> [1] https://lore.kernel.org/patchwork/patch/1125789/
That is bloody unusable, don't do that. Use:
https://lkml.kernel.org/r/$MSGID
if anything. Then I can find it in my local mbox without having to
resort to touching a mouse and shitty browser software.
(also patchwork is absolute crap for reading email threads)
Anyway, I found it -- I think, I refused to click the link. I replied
there.
> Signed-off-by: Yunsheng Lin <linyunsheng@...wei.com>
> Suggested-by: Michal Hocko <mhocko@...nel.org>
> Acked-by: Michal Hocko <mhocko@...e.com>
> diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
> index 4123100e..9859acb 100644
> --- a/arch/x86/mm/numa.c
> +++ b/arch/x86/mm/numa.c
> @@ -861,6 +861,9 @@ void numa_remove_cpu(int cpu)
> */
> const struct cpumask *cpumask_of_node(int node)
> {
> + if (node == NUMA_NO_NODE)
> + return cpu_online_mask;
This mandates the caller holds cpus_read_lock() or something, I'm pretty
sure that if I put:
lockdep_assert_cpus_held();
here, it comes apart real quick. Without holding the cpu hotplug lock,
the online mask is gibberish.
> +
> if ((unsigned)node >= nr_node_ids) {
> printk(KERN_WARNING
> "cpumask_of_node(%d): (unsigned)node >= nr_node_ids(%u)\n",
I still think this makes absolutely no sense what so ever.
Powered by blists - more mailing lists