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Date: Mon, 20 Oct 2014 19:39:21 -0700
From: Martin Kelly <martin@...tingkelly.com>
To: linux-kernel@...r.kernel.org, x86@...nel.org
CC: tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
akpm@...ux-foundation.org, rientjes@...gle.com,
david.vrabel@...rix.com, Martin Kelly <martkell@...zon.com>
Subject: Re: [PATCH] x86, e820: panic on sanitizing invalid memory map
On 10/17/2014 09:41 PM, Martin Kelly wrote:
> sanitize_e820_map returns two possible values:
> -1: Returned when either the provided memory map has length 1 (ok) or
> when the provided memory map is invalid (not ok).
> 0: Returned when the memory map was correctly sanitized.
>
> In addition, most code ignores the returned value, and none actually
> handles it (except possibly by panicking).
>
> This patch changes the behavior so that sanitize_e820_map is a void
> function. When the provided memory map has length 1 or it is sanitized
> (both ok cases), it returns nothing. If the provided memory map is
> invalid, then it panics.
>
> Signed-off-by: Martin Kelly <martkell@...zon.com>
> ---
> arch/x86/include/asm/e820.h | 2 +-
> arch/x86/kernel/e820.c | 95 ++++++++++++++++++++++-----------------------
> 2 files changed, 47 insertions(+), 50 deletions(-)
>
> diff --git a/arch/x86/include/asm/e820.h b/arch/x86/include/asm/e820.h
> index 779c2ef..739f8db 100644
> --- a/arch/x86/include/asm/e820.h
> +++ b/arch/x86/include/asm/e820.h
> @@ -18,7 +18,7 @@ extern int e820_any_mapped(u64 start, u64 end, unsigned type);
> extern int e820_all_mapped(u64 start, u64 end, unsigned type);
> extern void e820_add_region(u64 start, u64 size, int type);
> extern void e820_print_map(char *who);
> -extern int
> +extern void
> sanitize_e820_map(struct e820entry *biosmap, int max_nr_map, u32 *pnr_map);
> extern u64 e820_update_range(u64 start, u64 size, unsigned old_type,
> unsigned new_type);
> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> index 49f8864..96ad559 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -188,47 +188,48 @@ void __init e820_print_map(char *who)
> * be updated on return, with the new number of valid entries
> * (something no more than max_nr_map.)
> *
> - * The return value from sanitize_e820_map() is zero if it
> - * successfully 'sanitized' the map entries passed in, and is -1
> - * if it did nothing, which can happen if either of (1) it was
> - * only passed one map entry, or (2) any of the input map entries
> - * were invalid (start + size < start, meaning that the size was
> - * so big the described memory range wrapped around through zero.)
> + * There are three possible actions that sanitize_e820_map() can take:
> + * (1) If the map entry count is 1, do nothing and return.
> + * (2) If any of the input map entries were invalid
> + * (start + size < start), then the size was so big that the described
> + * memory range wrapped around through zero. In this case, panic.
> + * (3) If the map entry count is greater than 1 and the map is valid,
> + * sanitize the map and return.
> *
> - * Visually we're performing the following
> - * (1,2,3,4 = memory types)...
> + * Visually we're performing the following
> + * (1,2,3,4 = memory types)...
> *
> - * Sample memory map (w/overlaps):
> - * ____22__________________
> - * ______________________4_
> - * ____1111________________
> - * _44_____________________
> - * 11111111________________
> - * ____________________33__
> - * ___________44___________
> - * __________33333_________
> - * ______________22________
> - * ___________________2222_
> - * _________111111111______
> - * _____________________11_
> - * _________________4______
> + * Sample memory map (w/overlaps):
> + * ____22__________________
> + * ______________________4_
> + * ____1111________________
> + * _44_____________________
> + * 11111111________________
> + * ____________________33__
> + * ___________44___________
> + * __________33333_________
> + * ______________22________
> + * ___________________2222_
> + * _________111111111______
> + * _____________________11_
> + * _________________4______
> *
> - * Sanitized equivalent (no overlap):
> - * 1_______________________
> - * _44_____________________
> - * ___1____________________
> - * ____22__________________
> - * ______11________________
> - * _________1______________
> - * __________3_____________
> - * ___________44___________
> - * _____________33_________
> - * _______________2________
> - * ________________1_______
> - * _________________4______
> - * ___________________2____
> - * ____________________33__
> - * ______________________4_
> + * Sanitized equivalent (no overlap):
> + * 1_______________________
> + * _44_____________________
> + * ___1____________________
> + * ____22__________________
> + * ______11________________
> + * _________1______________
> + * __________3_____________
> + * ___________44___________
> + * _____________33_________
> + * _______________2________
> + * ________________1_______
> + * _________________4______
> + * ___________________2____
> + * ____________________33__
> + * ______________________4_
> */
> struct change_member {
> struct e820entry *pbios; /* pointer to original bios entry */
> @@ -252,7 +253,7 @@ static int __init cpcompare(const void *a, const void *b)
> return (ap->addr != ap->pbios->addr) - (bp->addr != bp->pbios->addr);
> }
>
> -int __init sanitize_e820_map(struct e820entry *biosmap, int max_nr_map,
> +void __init sanitize_e820_map(struct e820entry *biosmap, int max_nr_map,
> u32 *pnr_map)
> {
> static struct change_member change_point_list[2*E820_X_MAX] __initdata;
> @@ -269,15 +270,14 @@ int __init sanitize_e820_map(struct e820entry *biosmap, int max_nr_map,
>
> /* if there's only one memory region, don't bother */
> if (*pnr_map < 2)
> - return -1;
> + return;
>
> old_nr = *pnr_map;
> BUG_ON(old_nr > max_nr_map);
>
> - /* bail out if we find any unreasonable addresses in bios map */
> + /* panic if we find any unreasonable addresses in bios map */
> for (i = 0; i < old_nr; i++)
> - if (biosmap[i].addr + biosmap[i].size < biosmap[i].addr)
> - return -1;
> + BUG_ON(biosmap[i].addr + biosmap[i].size < biosmap[i].addr);
>
> /* create pointers for initial change-point information (for sorting) */
> for (i = 0; i < 2 * old_nr; i++)
> @@ -564,8 +564,7 @@ void __init update_e820(void)
> u32 nr_map;
>
> nr_map = e820.nr_map;
> - if (sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &nr_map))
> - return;
> + sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &nr_map);
> e820.nr_map = nr_map;
> printk(KERN_INFO "e820: modified physical RAM map:\n");
> e820_print_map("modified");
> @@ -575,8 +574,7 @@ static void __init update_e820_saved(void)
> u32 nr_map;
>
> nr_map = e820_saved.nr_map;
> - if (sanitize_e820_map(e820_saved.map, ARRAY_SIZE(e820_saved.map), &nr_map))
> - return;
> + sanitize_e820_map(e820_saved.map, ARRAY_SIZE(e820_saved.map), &nr_map);
> e820_saved.nr_map = nr_map;
> }
> #define MAX_GAP_END 0x100000000ull
> @@ -900,8 +898,7 @@ void __init finish_e820_parsing(void)
> if (userdef) {
> u32 nr = e820.nr_map;
>
> - if (sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &nr) < 0)
> - early_panic("Invalid user supplied memory map");
> + sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &nr);
> e820.nr_map = nr;
>
> printk(KERN_INFO "e820: user-defined physical RAM map:\n");
>
I noticed some compiler warnings from this patch; I fixed them and sent
a revision.
--
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