linux-kernel - [PATCH] dm: Allow the use of escaped characters in str_field

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Message-ID: <20241112175758.114080-1-pvmohammedanees2003@gmail.com>
Date: Tue, 12 Nov 2024 23:27:58 +0530
From: Mohammed Anees <pvmohammedanees2003@...il.com>
To: Alasdair Kergon <agk@...hat.com>,
	Mike Snitzer <snitzer@...nel.org>,
	Mikulas Patocka <mpatocka@...hat.com>
Cc: dm-devel@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	Mohammed Anees <pvmohammedanees2003@...il.com>
Subject: [PATCH] dm: Allow the use of escaped characters in str_field_delimit()

Escape characters were not handled before, which could lead to
unwanted issues. Some device-mapper names may contain backslashes (`\`)
as valid characters and should not be treated as escape characters. Only
escape characters followed directly by the separator are considered
valid and need to be processed. After handling, the escape characters
are removed to ensure the final string is correctly parsed without
unwanted escape sequences which were used only for escaping.

Signed-off-by: Mohammed Anees <pvmohammedanees2003@...il.com>
---
 drivers/md/dm-init.c | 28 ++++++++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/md/dm-init.c b/drivers/md/dm-init.c
index b37bbe762500..dad9d523f7fb 100644
--- a/drivers/md/dm-init.c
+++ b/drivers/md/dm-init.c
@@ -88,13 +88,33 @@ static void __init dm_setup_cleanup(struct list_head *devices)
 static char __init *str_field_delimit(char **str, char separator)
 {
 	char *s;
+	/* This variable handles removing escape characters, which are
+	 * only used to avoid the separator and aren't needed in the
+	 * final string.
+	 */
+	char *write;
 
-	/* TODO: add support for escaped characters */
 	*str = skip_spaces(*str);
-	s = strchr(*str, separator);
+	s = *str;
+	write = *str;
+
+	/* Find the separator and handle escape character */
+	while (*s) {
+		/* If '\' is followed by the separator, skip '\' by
+		 * incrementing s, write will then overwrite the
+		 * escape character with the separator.
+		 */
+		if (*s == '\\' && *(s + 1) != '\0' && *(s + 1) == separator)
+			s++;
+		else if (*s == separator)
+			break;
+
+		*write++ = *s++;
+	}
+
 	/* Delimit the field and remove trailing spaces */
-	if (s)
-		*s = '\0';
+	if (write)
+		*write = '\0';
 	*str = strim(*str);
 	return s ? ++s : NULL;
 }
-- 
2.47.0