Commit-ID: 00e5a2bbcc31d5fea853f8daeba0f06c1c88c3ff
Gitweb: https://git.kernel.org/tip/00e5a2bbcc31d5fea853f8daeba0f06c1c88c3ff
Author: Baoquan He <b...@redhat.com>
AuthorDate: Thu, 23 May 2019 10:57:44 +0800
Committer: Borislav Petkov <b...@suse.de>
CommitDate: Fri, 7 Jun 2019 23:12:13 +0200
x86/mm/KASLR: Compute the size of the vmemmap section properly
The size of the vmemmap section is hardcoded to 1 TB to support the
maximum amount of system RAM in 4-level paging mode - 64 TB.
However, 1 TB is not enough for vmemmap in 5-level paging mode. Assuming
the size of struct page is 64 Bytes, to support 4 PB system RAM in 5-level,
64 TB of vmemmap area is needed:
4 * 1000^5 PB / 4096 bytes page size * 64 bytes per page struct / 1000^4 TB =
62.5 TB.
This hardcoding may cause vmemmap to corrupt the following
cpu_entry_area section, if KASLR puts vmemmap very close to it and the
actual vmemmap size is bigger than 1 TB.
So calculate the actual size of the vmemmap region needed and then align
it up to 1 TB boundary.
In 4-level paging mode it is always 1 TB. In 5-level it's adjusted on
demand. The current code reserves 0.5 PB for vmemmap on 5-level. With
this change, the space can be saved and thus used to increase entropy
for the randomization.
[ bp: Spell out how the 64 TB needed for vmemmap is computed and massage commit
message. ]
Fixes: eedb92abb9bb ("x86/mm: Make virtual memory layout dynamic for
CONFIG_X86_5LEVEL=y")
Signed-off-by: Baoquan He <b...@redhat.com>
Signed-off-by: Borislav Petkov <b...@suse.de>
Reviewed-by: Kees Cook <keesc...@chromium.org>
Acked-by: Kirill A. Shutemov <kir...@linux.intel.com>
Cc: Andy Lutomirski <l...@kernel.org>
Cc: Dave Hansen <dave.han...@linux.intel.com>
Cc: "H. Peter Anvin" <h...@zytor.com>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: kirill.shute...@linux.intel.com
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: stable <sta...@vger.kernel.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: x86-ml <x...@kernel.org>
Link: https://lkml.kernel.org/r/20190523025744.3756-1-...@redhat.com
---
arch/x86/mm/kaslr.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c
index dc3f058bdf9b..dc6182eecefa 100644
--- a/arch/x86/mm/kaslr.c
+++ b/arch/x86/mm/kaslr.c
@@ -52,7 +52,7 @@ static __initdata struct kaslr_memory_region {
} kaslr_regions[] = {
{ &page_offset_base, 0 },
{ &vmalloc_base, 0 },
- { &vmemmap_base, 1 },
+ { &vmemmap_base, 0 },
};
/* Get size in bytes used by the memory region */
@@ -78,6 +78,7 @@ void __init kernel_randomize_memory(void)
unsigned long rand, memory_tb;
struct rnd_state rand_state;
unsigned long remain_entropy;
+ unsigned long vmemmap_size;
vaddr_start = pgtable_l5_enabled() ? __PAGE_OFFSET_BASE_L5 :
__PAGE_OFFSET_BASE_L4;
vaddr = vaddr_start;
@@ -109,6 +110,14 @@ void __init kernel_randomize_memory(void)
if (memory_tb < kaslr_regions[0].size_tb)
kaslr_regions[0].size_tb = memory_tb;
+ /*
+ * Calculate the vmemmap region size in TBs, aligned to a TB
+ * boundary.
+ */
+ vmemmap_size = (kaslr_regions[0].size_tb << (TB_SHIFT - PAGE_SHIFT)) *
+ sizeof(struct page);
+ kaslr_regions[2].size_tb = DIV_ROUND_UP(vmemmap_size, 1UL << TB_SHIFT);
+
/* Calculate entropy available between regions */
remain_entropy = vaddr_end - vaddr_start;
for (i = 0; i < ARRAY_SIZE(kaslr_regions); i++)
