linux-kernel - [PATCH 4.9 10/97] arm64: Enforce BBM for huge IO/VMAP mappings

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Message-Id: <20200122092757.442779817@linuxfoundation.org>
Date:   Wed, 22 Jan 2020 10:28:14 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hanjun Guo <hanjun.guo@...aro.org>,
        Lei Li <lious.lilei@...ilicon.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Ben Hutchings <ben.hutchings@...ethink.co.uk>
Subject: [PATCH 4.9 10/97] arm64: Enforce BBM for huge IO/VMAP mappings

From: Will Deacon <will.deacon@....com>

commit 15122ee2c515a253b0c66a3e618bc7ebe35105eb upstream.

ioremap_page_range doesn't honour break-before-make and attempts to put
down huge mappings (using p*d_set_huge) over the top of pre-existing
table entries. This leads to us leaking page table memory and also gives
rise to TLB conflicts and spurious aborts, which have been seen in
practice on Cortex-A75.

Until this has been resolved, refuse to put block mappings when the
existing entry is found to be present.

Fixes: 324420bf91f60 ("arm64: add support for ioremap() block mappings")
Reported-by: Hanjun Guo <hanjun.guo@...aro.org>
Reported-by: Lei Li <lious.lilei@...ilicon.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Signed-off-by: Will Deacon <will.deacon@....com>
Signed-off-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Ben Hutchings <ben.hutchings@...ethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/arm64/mm/mmu.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -799,6 +799,11 @@ int pud_set_huge(pud_t *pudp, phys_addr_
 {
 	pgprot_t sect_prot = __pgprot(PUD_TYPE_SECT |
 					pgprot_val(mk_sect_prot(prot)));
+
+	/* ioremap_page_range doesn't honour BBM */
+	if (pud_present(READ_ONCE(*pudp)))
+		return 0;
+
 	BUG_ON(phys & ~PUD_MASK);
 	set_pud(pudp, pfn_pud(__phys_to_pfn(phys), sect_prot));
 	return 1;
@@ -808,6 +813,11 @@ int pmd_set_huge(pmd_t *pmdp, phys_addr_
 {
 	pgprot_t sect_prot = __pgprot(PMD_TYPE_SECT |
 					pgprot_val(mk_sect_prot(prot)));
+
+	/* ioremap_page_range doesn't honour BBM */
+	if (pmd_present(READ_ONCE(*pmdp)))
+		return 0;
+
 	BUG_ON(phys & ~PMD_MASK);
 	set_pmd(pmdp, pfn_pmd(__phys_to_pfn(phys), sect_prot));
 	return 1;