linux-kernel - Re: [PATCH v2] dm: Add support for escaped characters in str_field

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Message-ID: <ZoQphjlssygSBiRr@redhat.com>
Date: Tue, 2 Jul 2024 12:23:34 -0400
From: Benjamin Marzinski <bmarzins@...hat.com>
To: Mikulas Patocka <mpatocka@...hat.com>
Cc: Abhinav Jain <jain.abhinav177@...il.com>, agk@...hat.com,
        snitzer@...nel.org, dm-devel@...ts.linux.dev,
        linux-kernel@...r.kernel.org, skhan@...uxfoundation.org,
        javier.carrasco.cruz@...il.com
Subject: Re: [PATCH v2] dm: Add support for escaped characters in
 str_field_delimit()

On Tue, Jul 02, 2024 at 05:18:38PM +0200, Mikulas Patocka wrote:
> Hi
> 
> I'd like to ask why is this needed. AFAIK, none of the allowed targets use 
> ',' on their table line.

',' and ';' are both legal characters in DM names and UUIDs, although I
can't think of a good reason why anyone would want to use them.

-Ben

> 
> Mikulas
> 
> 
> On Thu, 13 Jun 2024, Abhinav Jain wrote:
> 
> > Remove all the escape characters that come before separator.
> > Tested this code by writing a dummy program containing the two
> > functions and testing it on below input, sharing results:
> > 
> > Original string: "field1\,with\,commas,field2\,with\,more\,commas"
> > Field: "field1"
> > Field: "with"
> > Field: "commas"
> > Field: "field2"
> > Field: "with"
> > Field: "more"
> > Field: "commas"
> > 
> > Signed-off-by: Abhinav Jain <jain.abhinav177@...il.com>
> > ---
> > PATCH v1:
> > https://lore.kernel.org/all/20240609141721.52344-1-jain.abhinav177@gmail.com/
> > 
> > Changes since v1:
> >  - Modified the str_field_delimit function as per shared feedback
> >  - Added remove_escaped_characters function
> > ---
> > ---
> >  drivers/md/dm-init.c | 53 +++++++++++++++++++++++++++++++++++++++-----
> >  1 file changed, 47 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/md/dm-init.c b/drivers/md/dm-init.c
> > index 2a71bcdba92d..0e31ecf1b48e 100644
> > --- a/drivers/md/dm-init.c
> > +++ b/drivers/md/dm-init.c
> > @@ -76,6 +76,24 @@ static void __init dm_setup_cleanup(struct list_head *devices)
> >  	}
> >  }
> >  
> > +/* Remove escape characters from a given field string. */
> > +static void __init remove_escape_characters(char *field)
> > +{
> > +	char *src = field;
> > +	char *dest = field;
> > +
> > +	while (*src) {
> > +		if (*src == '\\') {
> > +			src++;
> > +			if (*src)
> > +				*dest++ = *src++;
> > +		} else {
> > +			*dest++ = *src++;
> > +		}
> > +	}
> > +	*dest = '\0';
> > +}
> > +
> >  /**
> >   * str_field_delimit - delimit a string based on a separator char.
> >   * @str: the pointer to the string to delimit.
> > @@ -87,16 +105,39 @@ static void __init dm_setup_cleanup(struct list_head *devices)
> >   */
> >  static char __init *str_field_delimit(char **str, char separator)
> >  {
> > -	char *s;
> > +	char *s, *escaped, *field;
> >  
> > -	/* TODO: add support for escaped characters */
> >  	*str = skip_spaces(*str);
> >  	s = strchr(*str, separator);
> > -	/* Delimit the field and remove trailing spaces */
> > -	if (s)
> > +
> > +	/* Check for escaped character */
> > +	escaped = strchr(*str, '\\');
> > +	while (escaped && (s == NULL || escaped < s)) {
> > +		/*
> > +		 * Move the separator search ahead if escaped
> > +		 * character comes before.
> > +		 */
> > +		s = strchr(escaped + 1, separator);
> > +		escaped = strchr(escaped + 1, '\\');
> > +	}
> > +
> > +	/* If we found a separator, we need to handle escape characters */
> > +	if (s) {
> > +		*s = '\0';
> > +
> > +		remove_escape_characters(*str);
> > +		field = *str;
> > +		*str = s + 1;
> > +	} else {
> > +		/* Handle the last field when no separator is present */
> > +		s = *str + strlen(*str);
> >  		*s = '\0';
> > -	*str = strim(*str);
> > -	return s ? ++s : NULL;
> > +
> > +		remove_escape_characters(*str);
> > +		field = *str;
> > +		*str = s;
> > +	}
> > +	return field;
> >  }
> >  
> >  /**
> > -- 
> > 2.34.1
> >