linux-kernel - Re: Nokia N900: insecure W+X mapping at 0xd0050000

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Date:   Thu, 8 Mar 2018 08:46:52 -0800
From:   Tony Lindgren <tony@...mide.com>
To:     Pavel Machek <pavel@....cz>
Cc:     pali.rohar@...il.com, sre@...nel.org,
        kernel list <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-omap@...r.kernel.org, khilman@...nel.org,
        aaro.koskinen@....fi, ivo.g.dimitrov.75@...il.com,
        patrikbachan@...il.com, serge@...lyn.com, abcloriens@...il.com,
        clayton@...ftyguy.net, martijn@...xit.nl,
        sakari.ailus@...ux.intel.com,
        Filip Matijević <filip.matijevic.pz@...il.com>,
        Dave Gerlach <d-gerlach@...com>
Subject: Re: Nokia N900: insecure W+X mapping at 0xd0050000

* Tony Lindgren <tony@...mide.com> [180308 16:25]:
> * Pavel Machek <pavel@....cz> [180308 06:29]:
> > Insecure W+X mappings, who cares about those? I have 7 pages...
> 
> Is this with CONFIG_DEBUG_WX=y?
> 
> My guess is that it's for mapping the PM assembly to SRAM. This
> is already fixed for am335x that is using drivers/misc/sram*.c.
> I think omap2 - omap4 still need fixing if this is the culprit.

Adding Dave to Cc, here's a quick fix for this one.

Regards,

Tony

8< -------------------
>From tony Mon Sep 17 00:00:00 2001
From: Tony Lindgren <tony@...mide.com>
Date: Thu, 8 Mar 2018 08:41:16 -0800
Subject: [PATCH] ARM: OMAP: Fix SRAM W+X mapping

We are still using custom SRAM code for some SoCs and are not marking
the PM code mapped to SRAM as read-only and executable after we're
done. With CONFIG_DEBUG_WX=y, we will get "Found insecure W+X mapping
at address" warning.

Let's fix this issue the same way as commit 728bbe75c82f ("misc: sram:
Introduce support code for protect-exec sram type") is doing for
drivers/misc/sram-exec.c.

Note that eventually we should be using sram-exec.c for all SoCs.

Cc: Dave Gerlach <d-gerlach@...com>
Reported-by: Pavel Machek <pavel@....cz>
Signed-off-by: Tony Lindgren <tony@...mide.com>
---
 arch/arm/plat-omap/sram.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/arch/arm/plat-omap/sram.c b/arch/arm/plat-omap/sram.c
--- a/arch/arm/plat-omap/sram.c
+++ b/arch/arm/plat-omap/sram.c
@@ -23,6 +23,7 @@
 #include <asm/fncpy.h>
 #include <asm/tlb.h>
 #include <asm/cacheflush.h>
+#include <asm/set_memory.h>
 
 #include <asm/mach/map.h>
 
@@ -96,3 +97,21 @@ void __init omap_map_sram(unsigned long start, unsigned long size,
 	memset_io(omap_sram_base + omap_sram_skip, 0,
 		  omap_sram_size - omap_sram_skip);
 }
+
+static int __init omap_sram_lock(void)
+{
+	unsigned long base;
+	int pages;
+
+	if (!omap_sram_base || !omap_sram_size)
+		return 0;
+
+	base = (unsigned long)omap_sram_base;
+	pages = PAGE_ALIGN(omap_sram_size) / PAGE_SIZE;
+
+	set_memory_ro((unsigned long)base, pages);
+	set_memory_x((unsigned long)base, pages);
+
+	return 0;
+}
+late_initcall(omap_sram_lock);
-- 
2.16.2