Commit ec12bc29 authored Oct 11, 2018 by Geert Uytterhoeven Committed by Petr Mladek Oct 12, 2018

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: ad67b74d ("printk: hash addresses printed with %p")
Link: http://lkml.kernel.org/r/20181011084249.4520-3-geert+renesas@glider.be


To: "Tobin C . Harding" <me@tobin.cc>
To: Andrew Morton <akpm@linux-foundation.org>
To: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>

parent 9073dac1

Documentation/core-api/printk-formats.rst

+2 −3

Original line number	Diff line number	Diff line
		@@ -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.

lib/vsprintf.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1563,7 +1563,7 @@ 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
		}
		}

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