linux-kernel - [PATCH 2/3] lib/vsprintf: Hash legacy clock addresses

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Date:   Mon,  8 Oct 2018 13:05:03 +0200
From:   Geert Uytterhoeven <geert+renesas@...der.be>
To:     Petr Mladek <pmladek@...e.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "Tobin C . Harding" <me@...in.cc>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>
Cc:     linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        Geert Uytterhoeven <geert+renesas@...der.be>
Subject: [PATCH 2/3] lib/vsprintf: Hash legacy clock addresses

On platforms using the Common Clock Framework, "%pC" prints the clock's
name. On legacy platforms, it prints the unhashed clock's address,
potentially leaking sensitive information regarding the kernel layout in
memory.

Avoid this leak by printing the hashed address instead.  To distinguish
between clocks, a 32-bit unique identifier is as good as an actual
pointer value.

Fixes: ad67b74d2469d9b8 ("printk: hash addresses printed with %p")
Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
---
 Documentation/core-api/printk-formats.rst | 5 ++---
 lib/vsprintf.c                            | 2 +-
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst
index 25dc591cb1108790..d39798c2558500d5 100644
--- a/Documentation/core-api/printk-formats.rst
+++ b/Documentation/core-api/printk-formats.rst
@@ -420,9 +420,8 @@ struct clk
 	%pC	pll1
 	%pCn	pll1
 
-For printing struct clk structures. %pC and %pCn print the name
-(Common Clock Framework) or address (legacy clock framework) of the
-structure.
+For printing struct clk structures. %pC and %pCn print the name of the clock
+(Common Clock Framework) or a unique 32-bit ID (legacy clock framework).
 
 Passed by reference.
 
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index b5bf90731c5a5277..1fb36260a44289e8 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1477,7 +1477,7 @@ char *clock(char *buf, char *end, struct clk *clk, struct printf_spec spec,
 #ifdef CONFIG_COMMON_CLK
 		return string(buf, end, __clk_get_name(clk), spec);
 #else
-		return special_hex_number(buf, end, (unsigned long)clk, sizeof(unsigned long));
+		return ptr_to_id(buf, end, clk, spec);
 #endif
 	}
 }
-- 
2.17.1