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Subject[tip:x86/boot] x86/boot/KASLR: Limit KASLR to extract the kernel in immovable memory only
Commit-ID:  690eaa53205769fd5c0c36e3aa737a615135f969
Gitweb: https://git.kernel.org/tip/690eaa53205769fd5c0c36e3aa737a615135f969
Author: Chao Fan <fanc.fnst@cn.fujitsu.com>
AuthorDate: Wed, 23 Jan 2019 19:08:50 +0800
Committer: Borislav Petkov <bp@suse.de>
CommitDate: Fri, 1 Feb 2019 11:52:55 +0100

x86/boot/KASLR: Limit KASLR to extract the kernel in immovable memory only

KASLR may randomly choose a range which is located in movable memory
regions. As a result, this will break memory hotplug and make the
movable memory chosen by KASLR immovable.

Therefore, limit KASLR to choose memory regions in the immovable range
after consulting the SRAT table.

[ bp:
- Rewrite commit message.
- Trim comments.
]

Signed-off-by: Chao Fan <fanc.fnst@cn.fujitsu.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: caoj.fnst@cn.fujitsu.com
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: indou.takao@jp.fujitsu.com
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: kasong@redhat.com
Cc: Kees Cook <keescook@chromium.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: msys.mizuma@gmail.com
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190123110850.12433-8-fanc.fnst@cn.fujitsu.com
---
arch/x86/boot/compressed/kaslr.c | 71 +++++++++++++++++++++++++++++++++-------
arch/x86/boot/compressed/misc.h | 1 +
2 files changed, 61 insertions(+), 11 deletions(-)

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index b251572e77af..a2039afe14a7 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -97,6 +97,8 @@ static bool memmap_too_large;
/* Store memory limit specified by "mem=nn[KMG]" or "memmap=nn[KMG]" */
static unsigned long long mem_limit = ULLONG_MAX;

+/* Number of immovable memory regions */
+static int num_immovable_mem;

enum mem_avoid_index {
MEM_AVOID_ZO_RANGE = 0,
@@ -413,6 +415,9 @@ static void mem_avoid_init(unsigned long input, unsigned long input_size,
/* Mark the memmap regions we need to avoid */
handle_mem_options();

+ /* Enumerate the immovable memory regions */
+ num_immovable_mem = count_immovable_mem_regions();
+
#ifdef CONFIG_X86_VERBOSE_BOOTUP
/* Make sure video RAM can be used. */
add_identity_map(0, PMD_SIZE);
@@ -568,9 +573,9 @@ static unsigned long slots_fetch_random(void)
return 0;
}

-static void process_mem_region(struct mem_vector *entry,
- unsigned long minimum,
- unsigned long image_size)
+static void __process_mem_region(struct mem_vector *entry,
+ unsigned long minimum,
+ unsigned long image_size)
{
struct mem_vector region, overlap;
unsigned long start_orig, end;
@@ -646,6 +651,56 @@ static void process_mem_region(struct mem_vector *entry,
}
}

+static bool process_mem_region(struct mem_vector *region,
+ unsigned long long minimum,
+ unsigned long long image_size)
+{
+ int i;
+ /*
+ * If no immovable memory found, or MEMORY_HOTREMOVE disabled,
+ * use @region directly.
+ */
+ if (!num_immovable_mem) {
+ __process_mem_region(region, minimum, image_size);
+
+ if (slot_area_index == MAX_SLOT_AREA) {
+ debug_putstr("Aborted e820/efi memmap scan (slot_areas full)!\n");
+ return 1;
+ }
+ return 0;
+ }
+
+#ifdef CONFIG_MEMORY_HOTREMOVE
+ /*
+ * If immovable memory found, filter the intersection between
+ * immovable memory and @region.
+ */
+ for (i = 0; i < num_immovable_mem; i++) {
+ unsigned long long start, end, entry_end, region_end;
+ struct mem_vector entry;
+
+ if (!mem_overlaps(region, &immovable_mem[i]))
+ continue;
+
+ start = immovable_mem[i].start;
+ end = start + immovable_mem[i].size;
+ region_end = region->start + region->size;
+
+ entry.start = clamp(region->start, start, end);
+ entry_end = clamp(region_end, start, end);
+ entry.size = entry_end - entry.start;
+
+ __process_mem_region(&entry, minimum, image_size);
+
+ if (slot_area_index == MAX_SLOT_AREA) {
+ debug_putstr("Aborted e820/efi memmap scan when walking immovable regions(slot_areas full)!\n");
+ return 1;
+ }
+ }
+ return 0;
+#endif
+}
+
#ifdef CONFIG_EFI
/*
* Returns true if mirror region found (and must have been processed
@@ -711,11 +766,8 @@ process_efi_entries(unsigned long minimum, unsigned long image_size)

region.start = md->phys_addr;
region.size = md->num_pages << EFI_PAGE_SHIFT;
- process_mem_region(&region, minimum, image_size);
- if (slot_area_index == MAX_SLOT_AREA) {
- debug_putstr("Aborted EFI scan (slot_areas full)!\n");
+ if (process_mem_region(&region, minimum, image_size))
break;
- }
}
return true;
}
@@ -742,11 +794,8 @@ static void process_e820_entries(unsigned long minimum,
continue;
region.start = entry->addr;
region.size = entry->size;
- process_mem_region(&region, minimum, image_size);
- if (slot_area_index == MAX_SLOT_AREA) {
- debug_putstr("Aborted e820 scan (slot_areas full)!\n");
+ if (process_mem_region(&region, minimum, image_size))
break;
- }
}
}

diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 9911d11c5d09..19e8231a6fd6 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -132,6 +132,7 @@ static inline acpi_physical_address get_rsdp_addr(void) { return 0; }
#endif

#if defined(CONFIG_RANDOMIZE_BASE) && defined(CONFIG_MEMORY_HOTREMOVE)
+extern struct mem_vector immovable_mem[MAX_NUMNODES*2];
int count_immovable_mem_regions(void);
#else
static inline int count_immovable_mem_regions(void) { return 0; }
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