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authorBaoquan He <bhe@redhat.com>2019-05-23 10:57:44 +0800
committerPaul Gortmaker <paul.gortmaker@windriver.com>2019-09-16 12:21:26 -0400
commit63e9792a35560f9b40223301e3164d4991f57014 (patch)
tree9a370d3165dabd8178b0a6bd7140bb8c18940b6b
parent18d4e579fe7ac6717a8fab97a1c5aa8859f83124 (diff)
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x86/mm/KASLR: Compute the size of the vmemmap section properly
commit 00e5a2bbcc31d5fea853f8daeba0f06c1c88c3ff upstream. 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 <bhe@redhat.com> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Kirill A. Shutemov <kirill@linux.intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: kirill.shutemov@linux.intel.com Cc: Peter Zijlstra <peterz@infradead.org> Cc: stable <stable@vger.kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20190523025744.3756-1-bhe@redhat.com Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
-rw-r--r--arch/x86/mm/kaslr.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c
index 0988971069c9..bfe769209eae 100644
--- a/arch/x86/mm/kaslr.c
+++ b/arch/x86/mm/kaslr.c
@@ -51,7 +51,7 @@ 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 */
@@ -77,6 +77,7 @@ 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;
@@ -108,6 +109,14 @@ 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++)