linux-kernel - [PATCH 4.7 070/143] arm64: avoid TLB conflict with CONFIG_RANDOMIZE

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Message-Id: <20160905164433.574250885@linuxfoundation.org>
Date:   Mon,  5 Sep 2016 18:44:06 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>
Subject: [PATCH 4.7 070/143] arm64: avoid TLB conflict with CONFIG_RANDOMIZE_BASE

4.7-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mark Rutland <mark.rutland@....com>

commit fd363bd417ddb6103564c69cfcbd92d9a7877431 upstream.

When CONFIG_RANDOMIZE_BASE is selected, we modify the page tables to remap the
kernel at a newly-chosen VA range. We do this with the MMU disabled, but do not
invalidate TLBs prior to re-enabling the MMU with the new tables. Thus the old
mappings entries may still live in TLBs, and we risk violating
Break-Before-Make requirements, leading to TLB conflicts and/or other issues.

We invalidate TLBs when we uninsall the idmap in early setup code, but prior to
this we are subject to issues relating to the Break-Before-Make violation.

Avoid these issues by invalidating the TLBs before the new mappings can be
used by the hardware.

Fixes: f80fb3a3d508 ("arm64: add support for kernel ASLR")
Acked-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Acked-by: Will Deacon <will.deacon@....com>
Signed-off-by: Mark Rutland <mark.rutland@....com>
Signed-off-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/arm64/kernel/head.S |    3 +++
 1 file changed, 3 insertions(+)

--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -757,6 +757,9 @@ ENTRY(__enable_mmu)
 	isb
 	bl	__create_page_tables		// recreate kernel mapping

+	tlbi	vmalle1				// Remove any stale TLB entries
+	dsb	nsh
+
 	msr	sctlr_el1, x19			// re-enable the MMU
 	isb
 	ic	iallu				// flush instructions fetched