linux-kernel - [PATCH] ARM: memblock limit must be pmd-aligned

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Message-Id: <20170626172315.26369-1-opendmb@gmail.com>
Date:   Mon, 26 Jun 2017 10:23:15 -0700
From:   Doug Berger <opendmb@...il.com>
To:     linux@...linux.org.uk
Cc:     labbott@...hat.com, ard.biesheuvel@...aro.org,
        nicolas.pitre@...aro.org, tixy@...aro.org, f.fainelli@...il.com,
        keescook@...omium.org, marc.zyngier@....com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Doug Berger <opendmb@...il.com>
Subject: [PATCH] ARM: memblock limit must be pmd-aligned

There is a path through the adjust_lowmem_bounds() routine where if all
memory regions start and end on pmd-aligned addresses the memblock_limit
will be set to arm_lowmem_limit.

However, since arm_lowmem_limit can be affected by the vmalloc early
parameter, the value of arm_lowmem_limit may not be pmd-aligned. This
commit corrects this oversight such that memblock_limit is always rounded
down to pmd-alignment.

The pmd containing arm_lowmem_limit is cleared by prepare_page_table()
and without this commit it is possible for early_alloc() to allocate
unmapped memory in that range when mapping the lowmem.

Signed-off-by: Doug Berger <opendmb@...il.com>
---
 arch/arm/mm/mmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 31af3cb59a60..2ae4f9c9d757 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -1226,7 +1226,7 @@ void __init adjust_lowmem_bounds(void)
 	if (memblock_limit)
 		memblock_limit = round_down(memblock_limit, PMD_SIZE);
 	if (!memblock_limit)
-		memblock_limit = arm_lowmem_limit;
+		memblock_limit = round_down(arm_lowmem_limit, PMD_SIZE);

 	if (!IS_ENABLED(CONFIG_HIGHMEM) || cache_is_vipt_aliasing()) {
 		if (memblock_end_of_DRAM() > arm_lowmem_limit) {
-- 
2.13.0