mntent: unescape octal sequences

As entries in mtab are delimited by spaces, whitespace characters
are escaped as octal sequences. When reading them out, we have to
unescape these sequences to get the proper string.

src/misc/mntent.c

@@ -20,6 +20,42 @@ int endmntent(FILE *f)
 	return 1;
 }
 
+static char *unescape_ent(char *beg)
+{
+	char *dest = beg;
+	const char *src = beg;
+	while (*src) {
+		const char *val;
+		unsigned char cval = 0;
+		if (*src != '\\') {
+			*dest++ = *src++;
+			continue;
+		}
+		if (src[1] == '\\') {
+			++src;
+			*dest++ = *src++;
+			continue;
+		}
+		val = src + 1;
+		for (int i = 0; i < 3; ++i) {
+			if (*val >= '0' && *val <= '7') {
+				cval <<= 3;
+				cval += *val++ - '0';
+			} else {
+				break;
+			}
+		}
+		if (cval) {
+			*dest++ = cval;
+			src = val;
+		} else {
+			*dest++ = *src++;
+		}
+	}
+	*dest = 0;
+	return beg;
+}
+
 struct mntent *getmntent_r(FILE *f, struct mntent *mnt, char *linebuf, int buflen)
 {
 	int n[8], use_internal = (linebuf == SENTINEL);
@@ -55,10 +91,10 @@ struct mntent *getmntent_r(FILE *f, struct mntent *mnt, char *linebuf, int bufle
 	linebuf[n[5]] = 0;
 	linebuf[n[7]] = 0;
 
-	mnt->mnt_fsname = linebuf+n[0];
-	mnt->mnt_dir = linebuf+n[2];
-	mnt->mnt_type = linebuf+n[4];
-	mnt->mnt_opts = linebuf+n[6];
+	mnt->mnt_fsname = unescape_ent(linebuf+n[0]);
+	mnt->mnt_dir = unescape_ent(linebuf+n[2]);
+	mnt->mnt_type = unescape_ent(linebuf+n[4]);
+	mnt->mnt_opts = unescape_ent(linebuf+n[6]);
 
 	return mnt;
 }