From: Mike Rapoport <rppt@kernel.org>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Guillaume Tucker <gtucker@collabora.com>,
Mark Brown <broonie@kernel.org>,
Mark-PK Tsai <mark-pk.tsai@mediatek.com>,
Mike Rapoport <rppt@linux.ibm.com>,
Russell King <linux@armlinux.org.uk>,
Tony Lindgren <tony@atomide.com>, Will Deacon <will@kernel.org>,
"kernelci . org bot" <bot@kernelci.org>,
kernelci-results@groups.io,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
"# 3.4.x" <stable@vger.kernel.org>
Subject: Re: [PATCH] arm[64]/memremap: don't abuse pfn_valid() to ensure presence of linear map
Date: Mon, 25 Apr 2022 06:58:08 +0300 [thread overview]
Message-ID: <YmYcUEZfyk1FbJyW@kernel.org> (raw)
In-Reply-To: <CAMj1kXGzL2u1gOBs7EutZXXej-2-a+EouEZySXXsQ0Dz0gaKTA@mail.gmail.com>
On Sun, Apr 24, 2022 at 11:19:05PM +0200, Ard Biesheuvel wrote:
> On Sun, 24 Apr 2022 at 19:22, Mike Rapoport <rppt@kernel.org> wrote:
> >
> > From: Mike Rapoport <rppt@linux.ibm.com>
> >
> > The semantics of pfn_valid() is to check presence of the memory map for a
> > PFN and not whether a PFN is covered by the linear map. The memory map may
> > be present for NOMAP memory regions, but they won't be mapped in the linear
> > mapping. Accessing such regions via __va() when they are memremap()'ed
> > will cause a crash.
...
> > diff --git a/kernel/iomem.c b/kernel/iomem.c
> > index 62c92e43aa0d..e85bed24c0a9 100644
> > --- a/kernel/iomem.c
> > +++ b/kernel/iomem.c
> > @@ -33,7 +33,7 @@ static void *try_ram_remap(resource_size_t offset, size_t size,
> > unsigned long pfn = PHYS_PFN(offset);
> >
> > /* In the simple case just return the existing linear address */
> > - if (pfn_valid(pfn) && !PageHighMem(pfn_to_page(pfn)) &&
> > + if (!PageHighMem(pfn_to_page(pfn)) &&
>
> This looks wrong to me. Calling any of the PageXxx() accessors is only
> safe if the PFN is valid, since otherwise, we don't know if the
> associated struct page exists.
Yeah, you are right, was over-enthusiastic here...
> > arch_memremap_can_ram_remap(offset, size, flags))
> > return __va(offset);
> >
> >
> > base-commit: b2d229d4ddb17db541098b83524d901257e93845
> > --
> > 2.28.0
> >
--
Sincerely yours,
Mike.
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prev parent reply other threads:[~2022-04-25 3:59 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-24 17:20 [PATCH] arm[64]/memremap: don't abuse pfn_valid() to ensure presence of linear map Mike Rapoport
2022-04-24 20:14 ` kernel test robot
2022-04-24 20:14 ` kernel test robot
2022-04-24 21:19 ` Ard Biesheuvel
2022-04-25 3:58 ` Mike Rapoport [this message]
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