From: Karel Zak <kzak@redhat.com>
Date: Mon, 5 May 2025 11:04:54 +0000 (+0200)
Subject: libmount: add function to remove escaped chars
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=00e70d300c8e73a3c6a9e7398a48f780fc006f59;p=thirdparty%2Futil-linux.git

libmount: add function to remove escaped chars

Follow-up: 8a69fa852dd5f41f8456756d18bfac6d8208219f https://github.com/util-linux/util-linux/pull/3541
Signed-off-by: Karel Zak <kzak@redhat.com>
---

diff --git a/include/mangle.h b/include/mangle.h
index 59396916f..7deb8bed5 100644
--- a/include/mangle.h
+++ b/include/mangle.h
@@ -13,6 +13,7 @@ extern char *mangle(const char *s);
 
 extern void unmangle_to_buffer(const char *s, char *buf, size_t len);
 extern size_t unhexmangle_to_buffer(const char *s, char *buf, size_t len);
+extern size_t unescape_to_buffer(const char *s, const char *wanted, char *buf, size_t len);
 
 extern char *unmangle(const char *s, const char **end);
 
@@ -28,5 +29,11 @@ static inline void unhexmangle_string(char *s)
 		unhexmangle_to_buffer(s, s, strlen(s) + 1);
 }
 
+static inline void unescape_string(char *s, const char *wanted)
+{
+	if (s)
+		unescape_to_buffer(s, wanted, s, strlen(s) + 1);
+}
+
 #endif /* UTIL_LINUX_MANGLE_H */
 
diff --git a/lib/mangle.c b/lib/mangle.c
index 1a3b89ae4..2d31943cb 100644
--- a/lib/mangle.c
+++ b/lib/mangle.c
@@ -95,6 +95,25 @@ size_t unhexmangle_to_buffer(const char *s, char *buf, size_t len)
 	return buf - buf0 + 1;
 }
 
+size_t unescape_to_buffer(const char *s, const char *wanted, char *buf, size_t len)
+{
+	size_t sz = 0;
+	const char *buf0 = buf;
+
+	while (*s && sz < len - 1) {
+		if (*s == '\\' && sz + 1 < len - 1 && strchr(wanted, s[1])) {
+			*buf++ = s[1];
+			s += 2;
+			sz += 2;
+		} else {
+			*buf++ = *s++;;
+			sz++;
+		}
+	}
+	*buf = '\0';
+	return buf - buf0 + 1;
+}
+
 static inline const char *skip_nonspaces(const char *s)
 {
 	while (s && *s && !(*s == ' ' || *s == '\t'))
@@ -136,7 +155,7 @@ int main(int argc, char *argv[])
 {
 	char *p = NULL;
 	if (argc < 3) {
-		fprintf(stderr, "usage: %s --mangle|unmangle <string>\n",
+		fprintf(stderr, "usage: %s --mangle|unmangle|unescape <string>\n",
 						program_invocation_short_name);
 		return EXIT_FAILURE;
 	}
@@ -164,6 +183,16 @@ int main(int argc, char *argv[])
 		}
 	}
 
+	else if (!strcmp(argv[1], "--unescape")) {
+		char *x = strdup(argv[2]);
+		if (x) {
+			unescape_to_buffer(x, ",\"", x, strlen(x) + 1);
+
+			printf("self-unescaped: '%s'\n", x);
+			free(x);
+		}
+	}
+
 	return EXIT_SUCCESS;
 }
 #endif /* TEST_PROGRAM_MANGLE */
diff --git a/libmount/src/hook_mount.c b/libmount/src/hook_mount.c
index 9f722b27f..35f3a8d74 100644
--- a/libmount/src/hook_mount.c
+++ b/libmount/src/hook_mount.c
@@ -46,6 +46,7 @@
 #include "mountP.h"
 #include "fileutils.h"	/* statx() fallback */
 #include "strutils.h"
+#include "mangle.h"
 #include "linux_version.h"
 
 #ifdef USE_LIBMOUNT_MOUNTFD_SUPPORT
@@ -138,19 +139,12 @@ static inline int fsconfig_set_value(
 	int rc;
 	char *s = NULL;
 
-	/* "\," is a way to use comma in values, let's remove \ escape */
-	if (value && strstr(value, "\\,")) {
-		char *x, *p;
-
+	/* Remove \, and \" escapes, both supported by ul_optstr_next() */
+	if (value && strchr(value, '\\')) {
 		s = strdup(value);
 		if (!s)
-			return -EINVAL;
-		for (x = p = s; *x; p++, x++) {
-			if (*x == '\\' && *(x + 1) == ',')
-				x++;
-			*p = *x;
-		}
-		*p = '\0';
+			return -ENOMEM;
+		unescape_string(s, ",\"");
 		value = s;
 	}