Messages in this thread | | | Subject | Re: [PATCH v2] x86: fix kaslr and memmap collision | From | Dave Jiang <> | Date | Thu, 15 Dec 2016 15:10:38 -0700 |
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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@intel.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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