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Message-ID: <20181025001312.GA3159@worktop.c.hoisthospitality.com>
Date: Thu, 25 Oct 2018 02:13:12 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Igor Stoppa <igor.stoppa@...il.com>
Cc: Mimi Zohar <zohar@...ux.vnet.ibm.com>,
Kees Cook <keescook@...omium.org>,
Matthew Wilcox <willy@...radead.org>,
Dave Chinner <david@...morbit.com>,
James Morris <jmorris@...ei.org>, Michal Hocko <mhocko@...nel.org>,
kernel-hardening@...ts.openwall.com,
linux-integrity@...r.kernel.org,
linux-security-module@...r.kernel.org, igor.stoppa@...wei.com,
Dave Hansen <dave.hansen@...ux.intel.com>,
Jonathan Corbet <corbet@....net>, Laura Abbott <labbott@...hat.com>,
Will Deacon <will.deacon@....com>,
Boqun Feng <boqun.feng@...il.com>, Arnd Bergmann <arnd@...db.de>,
linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 16/17] prmem: pratomic-long
On Wed, Oct 24, 2018 at 12:35:03AM +0300, Igor Stoppa wrote:
> +static __always_inline
> +bool __pratomic_long_op(bool inc, struct pratomic_long_t *l)
> +{
> + struct page *page;
> + uintptr_t base;
> + uintptr_t offset;
> + unsigned long flags;
> + size_t size = sizeof(*l);
> + bool is_virt = __is_wr_after_init(l, size);
> +
> + if (WARN(!(is_virt || likely(__is_wr_pool(l, size))),
> + WR_ERR_RANGE_MSG))
> + return false;
> + local_irq_save(flags);
> + if (is_virt)
> + page = virt_to_page(l);
> + else
> + vmalloc_to_page(l);
> + offset = (~PAGE_MASK) & (uintptr_t)l;
> + base = (uintptr_t)vmap(&page, 1, VM_MAP, PAGE_KERNEL);
> + if (WARN(!base, WR_ERR_PAGE_MSG)) {
> + local_irq_restore(flags);
> + return false;
> + }
> + if (inc)
> + atomic_long_inc((atomic_long_t *)(base + offset));
> + else
> + atomic_long_dec((atomic_long_t *)(base + offset));
> + vunmap((void *)base);
> + local_irq_restore(flags);
> + return true;
> +
> +}
That's just hideously nasty.. and horribly broken.
We're not going to duplicate all these kernel interfaces wrapped in gunk
like that. Also, you _cannot_ call vunmap() with IRQs disabled. Clearly
you've never tested this with debug bits enabled.
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