linux-kernel - [PATCH 3.16 095/305] parisc: Fix map_pages() to not overwrite existing pte entries

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Message-ID: <lsq.1549201508.664167788@decadent.org.uk>
Date:   Sun, 03 Feb 2019 14:45:08 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Helge Deller" <deller@....de>
Subject: [PATCH 3.16 095/305] parisc: Fix map_pages() to not overwrite
 existing pte entries

3.16.63-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Helge Deller <deller@....de>

commit 3c229b3f2dd8133f61bb81d3cb018be92f4bba39 upstream.

Fix a long-existing small nasty bug in the map_pages() implementation which
leads to overwriting already written pte entries with zero, *if* map_pages() is
called a second time with an end address which isn't aligned on a pmd boundry.
This happens for example if we want to remap only the text segment read/write
in order to run alternative patching on the code. Exiting the loop when we
reach the end address fixes this.

Signed-off-by: Helge Deller <deller@....de>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/parisc/mm/init.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

--- a/arch/parisc/mm/init.c
+++ b/arch/parisc/mm/init.c
@@ -492,12 +492,8 @@ static void __init map_pages(unsigned lo
 #endif
 					pte = __mk_pte(address, pgprot);

-				if (address >= end_paddr) {
-					if (force)
-						break;
-					else
-						pte_val(pte) = 0;
-				}
+				if (address >= end_paddr)
+					break;

 				set_pte(pg_table, pte);