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Date: Fri, 15 Sep 2017 18:14:09 +0100
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Michal Suchanek <msuchanek@suse.de>
Cc: Jonathan Corbet <corbet@lwn.net>,
 Benjamin Herrenschmidt <benh@kernel.crashing.org>,
 Paul Mackerras <paulus@samba.org>, Michael Ellerman <mpe@ellerman.id.au>,
 Mauro Carvalho Chehab <mchehab@kernel.org>,
 Jani Nikula <jani.nikula@intel.com>,
 Kamlakant Patel <kamlakant.patel@broadcom.com>,
 Bamvor Jian Zhang <bamvor.zhangjian@linaro.org>,
 Tamara Diaconita <diaconitatamara@gmail.com>,
 Trond Myklebust <trond.myklebust@primarydata.com>,
 Hari Bathini <hbathini@linux.vnet.ibm.com>,
 Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>,
 Andrew Morton <akpm@linux-foundation.org>,
 Nicholas Piggin <npiggin@gmail.com>, Baoquan He <bhe@redhat.com>,
 Ilya Matveychikov <matvejchikov@gmail.com>,
 Ingo Molnar <mingo@kernel.org>, linux-doc@vger.kernel.org,
 linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 1/6] lib/cmdline.c: Add backslash support to kernel
 commandline parsing.
Message-ID: <20170915171409.GZ5426@ZenIV.linux.org.uk>
References: <4fabdf584ad18d6aae61e331f783a5020567f634.1505231820.git.msuchanek@suse.de>
 <28da60231eb848981e858fa33e3b7e33f8547111.1505494668.git.msuchanek@suse.de>
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On Fri, Sep 15, 2017 at 07:02:46PM +0200, Michal Suchanek wrote:

>  	for (i = 0; args[i]; i++) {
> -		if (isspace(args[i]) && !in_quote)
> +		if (isspace(args[i]) && !in_quote && !backslash)
>  			break;
> -		if (equals == 0) {
> -			if (args[i] == '=')
> -				equals = i;
> +
> +		if ((equals == 0) && (args[i] == '='))
> +			equals = i;
> +
> +		if (!backslash) {
> +			if ((args[i] == '"') || (args[i] == '\\')) {
> +				if (args[i] == '"')
> +					in_quote = !in_quote;
> +				if (args[i] == '\\')
> +					backslash = 1;
> +
> +				memmove(args + 1, args, i);
> +				args++;
> +				i--;
> +			}
> +		} else {
> +			backslash = 0;
>  		}
> -		if (args[i] == '"')
> -			in_quote = !in_quote;
>  	}

... and that makes for Unidiomatic Work With Strings Award for this September.
Using memmove() for string rewrite is almost always bad taste; in this case
it's also (as usual) broken.