linux-kernel - [PATCH] fix CONFIG_IO_STRICT_DEVMEM, do not enable by default

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Date:	Wed, 20 Jan 2016 14:37:22 -0800
From:	Dan Williams <dan.j.williams@...el.com>
To:	torvalds@...ux-foundation.org
Cc:	Russell King <linux@....linux.org.uk>,
	Kees Cook <keescook@...omium.org>,
	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Larry Finger <Larry.Finger@...inger.net>
Subject: [PATCH] fix CONFIG_IO_STRICT_DEVMEM, do not enable by default

Larry reports: "My PowerBook G4 Aluminum with a 32-bit PPC processor
fails to boot for the 4.4-git series".  This is likely due to X still
needing /dev/mem access on this platform.

CONFIG_IO_STRICT_DEVMEM is not yet safe to turn on when
CONFIG_STRICT_DEVMEM=y.  Remove the default so that old configurations
do not change behavior.

Fixes: 90a545e98126 ("restrict /dev/mem to idle io memory ranges")
Reported-by: Larry Finger <Larry.Finger@...inger.net>
Tested-by: Larry Finger <Larry.Finger@...inger.net>
Link: http://marc.info/?l=linux-kernel&m=145332012023825&w=2
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Russell King <linux@....linux.org.uk>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
 lib/Kconfig.debug |    1 -
 1 file changed, 1 deletion(-)

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index f75a33f29f6e..7d0b49c536c5 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1919,7 +1919,6 @@ config STRICT_DEVMEM
 config IO_STRICT_DEVMEM
 	bool "Filter I/O access to /dev/mem"
 	depends on STRICT_DEVMEM
-	default STRICT_DEVMEM
 	---help---
 	  If this option is disabled, you allow userspace (root) access to all
 	  io-memory regardless of whether a driver is actively using that