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Message-ID: <93dc229d-6362-f982-f9c8-8a0ca0bd8fb8@intel.com>
Date: Thu, 15 Dec 2016 15:10:38 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: tglx@...utronix.de, mingo@...hat.com, hpa@...or.com
Cc: dan.j.williams@...el.com, x86@...nel.org, david@...morbit.com,
linux-kernel@...r.kernel.org, linux-nvdimm@...ts.01.org
Subject: Re: [PATCH v2] x86: fix kaslr and memmap collision
On 11/29/2016 12:26 PM, Dave Jiang wrote:
> CONFIG_RANDOMIZE_BASE relocates the kernel to a random base address.
> However it does not take into account the memmap= parameter passed in from
> the kernel cmdline. This results in the kernel sometimes being put in
> the middle of the user memmap. Teaching kaslr to not insert the kernel in
> memmap defined regions. We will support up to 4 memmap regions. Any
> additional regions will cause kaslr to disable. The mem_avoid set has
> been augmented to add up to 4 regions of memmaps provided by the user
> to exclude those regions from the set of valid address range to insert
> the uncompressed kernel image.
>
> Signed-off-by: Dave Jiang <dave.jiang@...el.com>
Peter, Ingo, or Thomas,
Is this patch ok? Will someone be picking it up for 4.10? Thanks.
> ---
> arch/x86/boot/boot.h | 3 +
> arch/x86/boot/compressed/kaslr.c | 82 ++++++++++++++++++++++++++++++++++++++
> arch/x86/boot/string.c | 38 ++++++++++++++++++
> 3 files changed, 123 insertions(+)
>
> diff --git a/arch/x86/boot/boot.h b/arch/x86/boot/boot.h
> index e5612f3..59c2075 100644
> --- a/arch/x86/boot/boot.h
> +++ b/arch/x86/boot/boot.h
> @@ -332,7 +332,10 @@ int strncmp(const char *cs, const char *ct, size_t count);
> size_t strnlen(const char *s, size_t maxlen);
> unsigned int atou(const char *s);
> unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base);
> +unsigned long simple_strtoul(const char *cp, char **endp, unsigned int base);
> +long simple_strtol(const char *cp, char **endp, unsigned int base);
> size_t strlen(const char *s);
> +char *strchr(const char *s, int c);
>
> /* tty.c */
> void puts(const char *);
> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> index a66854d..915509f 100644
> --- a/arch/x86/boot/compressed/kaslr.c
> +++ b/arch/x86/boot/compressed/kaslr.c
> @@ -11,6 +11,7 @@
> */
> #include "misc.h"
> #include "error.h"
> +#include "../boot.h"
>
> #include <generated/compile.h>
> #include <linux/module.h>
> @@ -61,9 +62,16 @@ enum mem_avoid_index {
> MEM_AVOID_INITRD,
> MEM_AVOID_CMDLINE,
> MEM_AVOID_BOOTPARAMS,
> + MEM_AVOID_MEMMAP1,
> + MEM_AVOID_MEMMAP2,
> + MEM_AVOID_MEMMAP3,
> + MEM_AVOID_MEMMAP4,
> MEM_AVOID_MAX,
> };
>
> +/* only supporting at most 4 memmap regions with kaslr */
> +#define MAX_MEMMAP_REGIONS 4
> +
> static struct mem_vector mem_avoid[MEM_AVOID_MAX];
>
> static bool mem_overlaps(struct mem_vector *one, struct mem_vector *two)
> @@ -77,6 +85,72 @@ static bool mem_overlaps(struct mem_vector *one, struct mem_vector *two)
> return true;
> }
>
> +#include "../../../../lib/cmdline.c"
> +
> +static int
> +parse_memmap(char *p, unsigned long long *start, unsigned long long *size)
> +{
> + char *oldp;
> +
> + if (!p)
> + return -EINVAL;
> +
> + /* we don't care about this option here */
> + if (!strncmp(p, "exactmap", 8))
> + return -EINVAL;
> +
> + oldp = p;
> + *size = memparse(p, &p);
> + if (p == oldp)
> + return -EINVAL;
> +
> + switch (*p) {
> + case '@':
> + case '#':
> + case '$':
> + case '!':
> + *start = memparse(p + 1, &p);
> + return 0;
> + }
> +
> + return -EINVAL;
> +}
> +
> +static int mem_avoid_memmap(void)
> +{
> + char arg[128];
> + int rc = 0;
> +
> + /* see if we have any memmap areas */
> + if (cmdline_find_option("memmap", arg, sizeof(arg)) > 0) {
> + int i = 0;
> + char *str = arg;
> +
> + while (str && (i < MAX_MEMMAP_REGIONS)) {
> + unsigned long long start, size;
> + char *k = strchr(str, ',');
> +
> + if (k)
> + *k++ = 0;
> +
> + rc = parse_memmap(str, &start, &size);
> + if (rc < 0)
> + break;
> + str = k;
> +
> + mem_avoid[MEM_AVOID_MEMMAP1 + i].start = start;
> + mem_avoid[MEM_AVOID_MEMMAP1 + i].size = size;
> + i++;
> + }
> +
> + /* more than 4 memmaps, fail kaslr */
> + if ((i >= MAX_MEMMAP_REGIONS) && str)
> + rc = -EINVAL;
> + }
> +
> + return rc;
> +}
> +
> /*
> * In theory, KASLR can put the kernel anywhere in the range of [16M, 64T).
> * The mem_avoid array is used to store the ranges that need to be avoided
> @@ -429,6 +503,7 @@ void choose_random_location(unsigned long input,
> unsigned long *virt_addr)
> {
> unsigned long random_addr, min_addr;
> + int rc;
>
> /* By default, keep output position unchanged. */
> *virt_addr = *output;
> @@ -438,6 +513,13 @@ void choose_random_location(unsigned long input,
> return;
> }
>
> + /* Mark the memmap regions we need to avoid */
> + rc = mem_avoid_memmap();
> + if (rc < 0) {
> + warn("KASLR disabled: memmap exceeds limit of 4, giving up.");
> + return;
> + }
> +
> boot_params->hdr.loadflags |= KASLR_FLAG;
>
> /* Prepare to add new identity pagetables on demand. */
> diff --git a/arch/x86/boot/string.c b/arch/x86/boot/string.c
> index cc3bd58..0464aaa 100644
> --- a/arch/x86/boot/string.c
> +++ b/arch/x86/boot/string.c
> @@ -122,6 +122,31 @@ unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int bas
> }
>
> /**
> + * simple_strtoul - convert a string to an unsigned long
> + * @cp: The start of the string
> + * @endp: A pointer to the end of the parsed string will be placed here
> + * @base: The number base to use
> + */
> +unsigned long simple_strtoul(const char *cp, char **endp, unsigned int base)
> +{
> + return simple_strtoull(cp, endp, base);
> +}
> +
> +/**
> + * simple_strtol - convert a string to a signed long
> + * @cp: The start of the string
> + * @endp: A pointer to the end of the parsed string will be placed here
> + * @base: The number base to use
> + */
> +long simple_strtol(const char *cp, char **endp, unsigned int base)
> +{
> + if (*cp == '-')
> + return -simple_strtoul(cp + 1, endp, base);
> +
> + return simple_strtoul(cp, endp, base);
> +}
> +
> +/**
> * strlen - Find the length of a string
> * @s: The string to be sized
> */
> @@ -155,3 +180,16 @@ char *strstr(const char *s1, const char *s2)
> }
> return NULL;
> }
> +
> +/**
> + * strchr - Find the first occurrence of the character c in the string s.
> + * @s: the string to be searched
> + * @c: the character to search for
> + */
> +char *strchr(const char *s, int c)
> +{
> + while (*s != (char)c)
> + if (*s++ == '\0')
> + return NULL;
> + return (char *)s;
> +}
>
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