linux-kernel - [RFC 4/6] lib: vsprintf: default kptr

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Date:   Fri, 5 May 2017 21:07:37 -0700
From:   Greg KH <gregkh@...uxfoundation.org>
To:     kernel-hardening@...ts.openwall.com,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        William Roberts <william.c.roberts@...el.com>,
        Chris Fries <cfries@...gle.com>,
        Dave Weinstein <olorin@...gle.com>
Subject: [RFC 4/6] lib: vsprintf: default kptr_restrict to the maximum value

From: Dave Weinstein <olorin@...gle.com>

Set the initial value of kptr_restrict to the maximum
setting rather than the minimum setting, to ensure that
early boot logging is not leaking information.

Cc: William Roberts <william.c.roberts@...el.com>
Cc: Chris Fries <cfries@...gle.com>
Signed-off-by: Dave Weinstein <olorin@...gle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 lib/vsprintf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 75a49795fcae..404d477d4bd2 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -395,7 +395,7 @@ struct printf_spec {
 #define FIELD_WIDTH_MAX ((1 << 23) - 1)
 #define PRECISION_MAX ((1 << 15) - 1)
 
-int kptr_restrict __read_mostly;
+int kptr_restrict __read_mostly = 4;
 
 /*
  * Always cleanse %p and %pK specifiers
-- 
2.12.2