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SubjectRe: [PATCH v4 4/9] vsprintf: Consolidate handling of unknown pointer specifiers
On Wed, 2018-04-04 at 10:58 +0200, Petr Mladek wrote:
> There are few printk formats that make sense only with two or more
> specifiers. Also some specifiers make sense only when a kernel feature
> is enabled.
> The handling of unknown specifiers is strange, inconsistent, and
> even leaking the address. For example, netdev_bits() prints the
> non-hashed pointer value or clock() prints "(null)".
> The best solution seems to be in flags_string(). It does not print any
> misleading value. Instead it calls WARN_ONCE() describing the unknown
> specifier. Therefore it clearly shows the problem and helps to find
> it.
> Note that WARN_ONCE() used to cause recursive printk(). But it is safe
> now because vscnprintf() is called in printk_safe context from
> vprintk_emit().

> - if (!IS_ENABLED(CONFIG_HAVE_CLK) || !clk)
> + WARN_ONCE(1, "Unsupported pointer format specifier:
> %%pC\n");
> + return buf;
> + }
> +
> + if (!clk)
> return string(buf, end, NULL, spec);

This change collides with my patch series. Can you elaborate what your
thoughts are about my patches? Are you going incorporate them to your
series? Should I send them independently?

Andy Shevchenko <>
Intel Finland Oy

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