linux-kernel - [v6 11/15] arm64/kasan: explicitly zero kasan shadow memory

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Message-Id: <1502138329-123460-12-git-send-email-pasha.tatashin@oracle.com>
Date:   Mon,  7 Aug 2017 16:38:45 -0400
From:   Pavel Tatashin <pasha.tatashin@...cle.com>
To:     linux-kernel@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-mm@...ck.org, linuxppc-dev@...ts.ozlabs.org,
        linux-s390@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        x86@...nel.org, kasan-dev@...glegroups.com, borntraeger@...ibm.com,
        heiko.carstens@...ibm.com, davem@...emloft.net,
        willy@...radead.org, mhocko@...nel.org, ard.biesheuvel@...aro.org,
        will.deacon@....com, catalin.marinas@....com, sam@...nborg.org
Subject: [v6 11/15] arm64/kasan: explicitly zero kasan shadow memory

To optimize the performance of struct page initialization,
vmemmap_populate() will no longer zero memory.

We must explicitly zero the memory that is allocated by vmemmap_populate()
for kasan, as this memory does not go through struct page initialization
path.

Signed-off-by: Pavel Tatashin <pasha.tatashin@...cle.com>
Reviewed-by: Steven Sistare <steven.sistare@...cle.com>
Reviewed-by: Daniel Jordan <daniel.m.jordan@...cle.com>
Reviewed-by: Bob Picco <bob.picco@...cle.com>
---
 arch/arm64/mm/kasan_init.c | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index 81f03959a4ab..e78a9ecbb687 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -135,6 +135,41 @@ static void __init clear_pgds(unsigned long start,
 		set_pgd(pgd_offset_k(start), __pgd(0));
 }
 
+/*
+ * Memory that was allocated by vmemmap_populate is not zeroed, so we must
+ * zero it here explicitly.
+ */
+static void
+zero_vmemmap_populated_memory(void)
+{
+	struct memblock_region *reg;
+	u64 start, end;
+
+	for_each_memblock(memory, reg) {
+		start = __phys_to_virt(reg->base);
+		end = __phys_to_virt(reg->base + reg->size);
+
+		if (start >= end)
+			break;
+
+		start = (u64)kasan_mem_to_shadow((void *)start);
+		end = (u64)kasan_mem_to_shadow((void *)end);
+
+		/* Round to the start end of the mapped pages */
+		start = round_down(start, SWAPPER_BLOCK_SIZE);
+		end = round_up(end, SWAPPER_BLOCK_SIZE);
+		memset((void *)start, 0, end - start);
+	}
+
+	start = (u64)kasan_mem_to_shadow(_text);
+	end = (u64)kasan_mem_to_shadow(_end);
+
+	/* Round to the start end of the mapped pages */
+	start = round_down(start, SWAPPER_BLOCK_SIZE);
+	end = round_up(end, SWAPPER_BLOCK_SIZE);
+	memset((void *)start, 0, end - start);
+}
+
 void __init kasan_init(void)
 {
 	u64 kimg_shadow_start, kimg_shadow_end;
@@ -205,8 +240,15 @@ void __init kasan_init(void)
 			pfn_pte(sym_to_pfn(kasan_zero_page), PAGE_KERNEL_RO));
 
 	memset(kasan_zero_page, 0, PAGE_SIZE);
+
 	cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
 
+	/*
+	 * vmemmap_populate does not zero the memory, so we need to zero it
+	 * explicitly
+	 */
+	zero_vmemmap_populated_memory();
+
 	/* At this point kasan is fully initialized. Enable error messages */
 	init_task.kasan_depth = 0;
 	pr_info("KernelAddressSanitizer initialized\n");
-- 
2.14.0