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From:   Dan Williams <dan.j.williams@intel.com>
Date:   Tue, 31 Dec 2019 20:52:57 -0800
Message-ID: <CAPcyv4hXJi6v57L=-n8H9F_5Zvonr1idyijW7MqPdyMoGCj=2A@mail.gmail.com>
Subject: Re: [PATCH v2 3/4] efi: Fix efi_memmap_alloc() leaks
To:     Dave Young <dyoung@redhat.com>
Cc:     Ingo Molnar <mingo@redhat.com>,
        Taku Izumi <izumi.taku@jp.fujitsu.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-efi <linux-efi@vger.kernel.org>, kexec@lists.infradead.org,
        X86 ML <x86@kernel.org>
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On Tue, Dec 31, 2019 at 7:35 PM Dave Young <dyoung@redhat.com> wrote:
>
> Hi Dan,
> On 12/31/19 at 02:04pm, Dan Williams wrote:
> > With efi_fake_memmap() and efi_arch_mem_reserve() the efi table may be
> > updated and replaced multiple times. When that happens a previous
> > dynamically allocated efi memory map can be garbage collected. Use the
> > new EFI_MEMMAP_{SLAB,MEMBLOCK} flags to detect when a dynamically
> > allocated memory map is being replaced.
> >
> > Cc: Taku Izumi <izumi.taku@jp.fujitsu.com>
> > Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> > ---
> >  drivers/firmware/efi/memmap.c |   24 ++++++++++++++++++++++++
> >  1 file changed, 24 insertions(+)
> >
> > diff --git a/drivers/firmware/efi/memmap.c b/drivers/firmware/efi/memmap.c
> > index 2b81ee6858a9..188ab3cd5c52 100644
> > --- a/drivers/firmware/efi/memmap.c
> > +++ b/drivers/firmware/efi/memmap.c
> > @@ -29,6 +29,28 @@ static phys_addr_t __init __efi_memmap_alloc_late(unsigned long size)
> >       return PFN_PHYS(page_to_pfn(p));
> >  }
> >
> > +static void __init __efi_memmap_free(u64 phys, unsigned long size, unsigned long flags)
> > +{
> > +     if (WARN_ON(slab_is_available() && (flags & EFI_MEMMAP_MEMBLOCK)))
> > +             return;
> > +
> > +     if (flags & EFI_MEMMAP_MEMBLOCK) {
> > +             memblock_free(phys, size);
> > +     } else if (flags & EFI_MEMMAP_SLAB) {
> > +             struct page *p = pfn_to_page(PHYS_PFN(phys));
> > +             unsigned int order = get_order(size);
> > +
> > +             free_pages((unsigned long) page_address(p), order);
> > +     }
> > +}
> > +
> > +static void __init efi_memmap_free(void)
> > +{
> > +     __efi_memmap_free(efi.memmap.phys_map,
> > +                     efi.memmap.desc_size * efi.memmap.nr_map,
> > +                     efi.memmap.flags);
> > +}
> > +
> >  /**
> >   * efi_memmap_alloc - Allocate memory for the EFI memory map
> >   * @num_entries: Number of entries in the allocated map.
> > @@ -209,6 +231,8 @@ int __init efi_memmap_install(phys_addr_t addr, unsigned int nr_map,
> >       data.desc_size = efi.memmap.desc_size;
> >       flags |= efi.memmap.flags & EFI_MEMMAP_LATE;
> >
> > +     efi_memmap_free();
> > +
> >       return __efi_memmap_init(&data, flags);
>
> Hmm, only free the memmap in case __efi_memmap_init succeeded..

Ah true, that is a hastily chosen placement. Probably better in
__efi_memmap_init() after we're committed to the new map.