linux-kernel - Re: [PATCH v3] x86: avoid remapping data in parse_setup

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Message-ID: <CAE9FiQUyGH94SAz_g3RqciB275sK_QEHSogiex5O9GNRSaAj1A@mail.gmail.com>
Date:	Tue, 13 Aug 2013 15:22:40 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Linn Crosetto <linn@...com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"the arch/x86 maintainers" <x86@...nel.org>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	David Howells <dhowells@...hat.com>,
	Michael Kerrisk-manpages <mtk.manpages@...il.com>,
	Pekka Enberg <penberg@...nel.org>,
	Jacob Shin <jacob.shin@....com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] x86: avoid remapping data in parse_setup_data()

On Tue, Aug 13, 2013 at 2:46 PM, Linn Crosetto <linn@...com> wrote:
> Type SETUP_PCI, added by setup_efi_pci(), may advertise a ROM size
> larger than early_memremap() is able to handle, which is currently
> limited to 256kB. If this occurs it leads to a NULL dereference in
> parse_setup_data().
>
> To avoid this, remap the setup_data header and allow parsing functions
> for individual types to handle their own data remapping.
>
> Signed-off-by: Linn Crosetto <linn@...com>
> ---
> v3: Remove data remapping code from parse_setup_data() and add it to
> parse_e820_ext().

Acked-by: Yinghai Lu <yinghai@...nel.org>

>
>  arch/x86/include/asm/e820.h |  2 +-
>  arch/x86/kernel/e820.c      |  5 ++++-
>  arch/x86/kernel/setup.c     | 19 ++++++++-----------
>  3 files changed, 13 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/include/asm/e820.h b/arch/x86/include/asm/e820.h
> index cccd07f..779c2ef 100644
> --- a/arch/x86/include/asm/e820.h
> +++ b/arch/x86/include/asm/e820.h
> @@ -29,7 +29,7 @@ extern void e820_setup_gap(void);
>  extern int e820_search_gap(unsigned long *gapstart, unsigned long *gapsize,
>                         unsigned long start_addr, unsigned long long end_addr);
>  struct setup_data;
> -extern void parse_e820_ext(struct setup_data *data);
> +extern void parse_e820_ext(u64 phys_addr, u32 data_len);
>
>  #if defined(CONFIG_X86_64) || \
>         (defined(CONFIG_X86_32) && defined(CONFIG_HIBERNATION))
> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> index d32abea..174da5f 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -658,15 +658,18 @@ __init void e820_setup_gap(void)
>   * boot_params.e820_map, others are passed via SETUP_E820_EXT node of
>   * linked list of struct setup_data, which is parsed here.
>   */
> -void __init parse_e820_ext(struct setup_data *sdata)
> +void __init parse_e820_ext(u64 phys_addr, u32 data_len)
>  {
>         int entries;
>         struct e820entry *extmap;
> +       struct setup_data *sdata;
>
> +       sdata = early_memremap(phys_addr, data_len);
>         entries = sdata->len / sizeof(struct e820entry);
>         extmap = (struct e820entry *)(sdata->data);
>         __append_e820_map(extmap, entries);
>         sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);
> +       early_iounmap(sdata, data_len);
>         printk(KERN_INFO "e820: extended physical RAM map:\n");
>         e820_print_map("extended");
>  }
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index f8ec578..234e1e3 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -426,25 +426,23 @@ static void __init reserve_initrd(void)
>  static void __init parse_setup_data(void)
>  {
>         struct setup_data *data;
> -       u64 pa_data;
> +       u64 pa_data, pa_next;
>
>         pa_data = boot_params.hdr.setup_data;
>         while (pa_data) {
> -               u32 data_len, map_len;
> +               u32 data_len, map_len, data_type;
>
>                 map_len = max(PAGE_SIZE - (pa_data & ~PAGE_MASK),
>                               (u64)sizeof(struct setup_data));
>                 data = early_memremap(pa_data, map_len);
>                 data_len = data->len + sizeof(struct setup_data);
> -               if (data_len > map_len) {
> -                       early_iounmap(data, map_len);
> -                       data = early_memremap(pa_data, data_len);
> -                       map_len = data_len;
> -               }
> +               data_type = data->type;
> +               pa_next = data->next;
> +               early_iounmap(data, map_len);
>
> -               switch (data->type) {
> +               switch (data_type) {
>                 case SETUP_E820_EXT:
> -                       parse_e820_ext(data);
> +                       parse_e820_ext(pa_data, data_len);
>                         break;
>                 case SETUP_DTB:
>                         add_dtb(pa_data);
> @@ -452,8 +450,7 @@ static void __init parse_setup_data(void)
>                 default:
>                         break;
>                 }
> -               pa_data = data->next;
> -               early_iounmap(data, map_len);
> +               pa_data = pa_next;
>         }
>  }
--
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