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Date:   Fri, 19 Apr 2019 10:51:12 +0900
From:   Sergey Senozhatsky <>
To:     Petr Mladek <>
Cc:     Andy Shevchenko <>,
        Rasmus Villemoes <>,
        Linus Torvalds <>,
        "Tobin C . Harding" <>, Joe Perches <>,
        Andrew Morton <>,
        Michal Hocko <>,
        Sergey Senozhatsky <>,
        Steven Rostedt <>,
        Sergey Senozhatsky <>,
Subject: Re: [PATCH v7 00/10] vsprintf: Prevent silent crashes and
 consolidate error handling

On (04/17/19 13:53), Petr Mladek wrote:
> Crash in vsprintf() might be silent when it happens under logbuf_lock
> in vprintk_emit(). This patch set prevents most of the crashes by probing
> the address. The check is done only by %s and some %p* specifiers that need
> to dereference the address.
> Only the first byte of the address is checked to keep it simple. It should
> be enough to catch most problems.
> The check is explicitly done in each function that does the dereference.
> It helps to avoid the questionable strchr() of affected specifiers. This
> change motivated me to do some preparation patches that consolidated
> the error handling and cleaned the code a bit.

The patch set looks OK to me.

I got confused by 'pC?' error string, but once you start looking
at it as a regex (? - zero or one occurrences) things look OK.
Regex in dmesg/serial output might be something very new to people,
stack traces, after all, is a rather common error reporting mechanism.
So the previous "WARN_ON() + exact unrecognized fmt[N] char" was not
totally awful or wrong (well, it was, before we introduced printk_safe()),
but I don't have strong objections against that new regex thing.

Reviewed-by: Sergey Senozhatsky <>


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