From: Baoquan He <bhe@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: x86@kernel.org, tglx@linutronix.de, mingo@kernel.org,
bp@alien8.de, hpa@zytor.com, kirill@shutemov.name,
keescook@chromium.org, peterz@infradead.org, thgarnie@google.com,
herbert@gondor.apana.org.au, mike.travis@hpe.com,
frank.ramsay@hpe.com, yamada.masahiro@socionext.com,
Baoquan He <bhe@redhat.com>
Subject: [PATCH v2 2/2] x86/mm/KASLR: Fix the size of vmemmap section
Date: Fri, 12 Apr 2019 14:55:42 +0800 [thread overview]
Message-ID: <20190412065542.18431-3-bhe@redhat.com> (raw)
In-Reply-To: <20190412065542.18431-1-bhe@redhat.com>
kernel_randomize_memory() hardcodes the size of vmemmap section as 1 TB,
to support the maximum amount of system RAM in 4-level paging mode, 64 TB.
However, 1 TB is not enough 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. The wrong hardcoding may cause vmemmap stamping
into the following cpu_entry_area section, if KASLR puts vmemmap very close
to cpu_entry_area , and the needed area of vmemmap is much bigger than
1 TB.
So here calculate the actual size of vmemmap region, then align up to 1 TB
boundary. In 4-level it's always 1 TB. In 5-level it's adjusted on demand.
The current code reserves 0.5 PB for vmemmap in 5-level. In this way, the
left space can be saved to join randomization to increase the entropy.
Signed-off-by: Baoquan He <bhe@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 387d4ed25d7c..4679a0075048 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 how many TB vmemmap region needs, and aligned to
+ * 1TB 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++)
--
2.17.2
next prev parent reply other threads:[~2019-04-12 6:56 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-12 6:55 [PATCH v2 0/2] x86/mm/KASLR: Fix the wrong size of memory sections Baoquan He
2019-04-12 6:55 ` [PATCH v2 1/2] x86/mm/KASLR: Fix the size of the direct mapping section Baoquan He
2019-04-14 7:01 ` Baoquan He
2019-04-12 6:55 ` Baoquan He [this message]
2019-04-12 7:02 ` [PATCH v2 0/2] x86/mm/KASLR: Fix the wrong size of memory sections Baoquan He
2019-04-15 14:39 ` Kees Cook
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