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Date: Fri, 7 May 2021 16:27:27 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "shakeelb@...gle.com" <shakeelb@...gle.com>
CC: "kernel-hardening@...ts.openwall.com"
<kernel-hardening@...ts.openwall.com>, "luto@...nel.org" <luto@...nel.org>,
"Hansen, Dave" <dave.hansen@...el.com>, "x86@...nel.org" <x86@...nel.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>, "peterz@...radead.org"
<peterz@...radead.org>, "akpm@...ux-foundation.org"
<akpm@...ux-foundation.org>, "linux-kernel@...r.kernel.org"
<linux-kernel@...r.kernel.org>, "rppt@...nel.org" <rppt@...nel.org>,
"linux-hardening@...r.kernel.org" <linux-hardening@...r.kernel.org>, "Weiny,
Ira" <ira.weiny@...el.com>, "Williams, Dan J" <dan.j.williams@...el.com>
Subject: Re: [PATCH RFC 5/9] x86, mm: Use cache of page tables
On Thu, 2021-05-06 at 11:24 -0700, Shakeel Butt wrote:
> On Tue, May 4, 2021 at 5:36 PM Rick Edgecombe
> <rick.p.edgecombe@...el.com> wrote:
> >
> [...]
> > +#ifdef CONFIG_PKS_PG_TABLES
> > +struct page *alloc_table(gfp_t gfp)
> > +{
> > + struct page *table;
> > +
> > + if (!pks_page_en)
> > + return alloc_page(gfp);
> > +
> > + table = get_grouped_page(numa_node_id(), &gpc_pks);
> > + if (!table)
> > + return NULL;
> > +
> > + if (gfp & __GFP_ZERO)
> > + memset(page_address(table), 0, PAGE_SIZE);
> > +
> > + if (memcg_kmem_enabled() &&
> > + gfp & __GFP_ACCOUNT &&
> > + !__memcg_kmem_charge_page(table, gfp, 0)) {
> > + free_table(table);
> > + table = NULL;
> > + }
> > +
> > + VM_BUG_ON_PAGE(*(unsigned long *)&table->ptl, table);
>
> table can be NULL due to charge failure.
Argh, yes. Thank you. I'll remove the VM_BUG_ON, it was left
accidentally.
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