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x86/KASLR: Handle the memory limit specified by the 'memmap=' and 'mem=' boot options

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The 'mem=' boot option limits the max address a system can use - any memory
region above the limit will be removed.

Furthermore, the 'memmap=nn[KMG]' variant (with no offset specified) has the same
behaviour as 'mem='.

KASLR needs to consider this when choosing the random position for
decompressing the kernel. Do it.

Tested-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Signed-off-by: Baoquan He <bhe@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dan.j.williams@intel.com
Cc: douly.fnst@cn.fujitsu.com
Cc: dyoung@redhat.com
Link: http://lkml.kernel.org/r/1494654390-23861-3-git-send-email-bhe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Baoquan He 2017-05-13 13:46:29 +08:00 committed by Ingo Molnar
parent d52e7d5a95
commit 4cdba14f84
1 changed files with 50 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

68
arch/x86/boot/compressed/kaslr.c
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@ -88,6 +88,10 @@ struct mem_vector {
static bool memmap_too_large;
/* Store memory limit specified by "mem=nn[KMG]" or "memmap=nn[KMG]" */
unsigned long long mem_limit = ULLONG_MAX;
enum mem_avoid_index {
MEM_AVOID_ZO_RANGE = 0,
MEM_AVOID_INITRD,
@ -138,16 +142,23 @@ parse_memmap(char *p, unsigned long long *start, unsigned long long *size)
return -EINVAL;
switch (*p) {
case '@':
/* Skip this region, usable */
*start = 0;
*size = 0;
return 0;
case '#':
case '$':
case '!':
*start = memparse(p + 1, &p);
return 0;
case '@':
/* memmap=nn@ss specifies usable region, should be skipped */
*size = 0;
/* Fall through */
default:
/*
* If w/o offset, only size specified, memmap=nn[KMG] has the
* same behaviour as mem=nn[KMG]. It limits the max address
* system can use. Region above the limit should be avoided.
*/
*start = 0;
return 0;
}
return -EINVAL;
@ -173,9 +184,14 @@ static void mem_avoid_memmap(char *str)
if (rc < 0)
break;
str = k;
/* A usable region that should not be skipped */
if (size == 0)
if (start == 0) {
/* Store the specified memory limit if size > 0 */
if (size > 0)
mem_limit = size;
continue;
}
mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].start = start;
mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].size = size;
@ -187,19 +203,15 @@ static void mem_avoid_memmap(char *str)
memmap_too_large = true;
}
/*
* handle_mem_memmap will also cover 'mem=' issue in next patch. Will remove
* this note later.
*/
static int handle_mem_memmap(void)
{
char *args = (char *)get_cmd_line_ptr();
size_t len = strlen((char *)args);
char *tmp_cmdline;
char *param, *val;
u64 mem_size;
if (!strstr(args, "memmap="))
if (!strstr(args, "memmap=") && !strstr(args, "mem="))
return 0;
tmp_cmdline = malloc(len + 1);
@ -222,8 +234,20 @@ static int handle_mem_memmap(void)
return -1;
}
if (!strcmp(param, "memmap"))
if (!strcmp(param, "memmap")) {
mem_avoid_memmap(val);
} else if (!strcmp(param, "mem")) {
char *p = val;
if (!strcmp(p, "nopentium"))
continue;
mem_size = memparse(p, &p);
if (mem_size == 0) {
free(tmp_cmdline);
return -EINVAL;
}
mem_limit = mem_size;
}
}
free(tmp_cmdline);
@ -460,7 +484,8 @@ static void process_e820_entry(struct boot_e820_entry *entry,
{
struct mem_vector region, overlap;
struct slot_area slot_area;
unsigned long start_orig;
unsigned long start_orig, end;
struct boot_e820_entry cur_entry;
/* Skip non-RAM entries. */
if (entry->type != E820_TYPE_RAM)
@ -474,8 +499,15 @@ static void process_e820_entry(struct boot_e820_entry *entry,
if (entry->addr + entry->size < minimum)
return;
region.start = entry->addr;
region.size = entry->size;
/* Ignore entries above memory limit */
end = min(entry->size + entry->addr, mem_limit);
if (entry->addr >= end)
return;
cur_entry.addr = entry->addr;
cur_entry.size = end - entry->addr;
region.start = cur_entry.addr;
region.size = cur_entry.size;
/* Give up if slot area array is full. */
while (slot_area_index < MAX_SLOT_AREA) {
@ -489,7 +521,7 @@ static void process_e820_entry(struct boot_e820_entry *entry,
region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);
/* Did we raise the address above this e820 region? */
if (region.start > entry->addr + entry->size)
if (region.start > cur_entry.addr + cur_entry.size)
return;
/* Reduce size by any delta from the original address. */