On Aug 8, 2021, at 9:24 AM, Pali Rohár [off-list ref] wrote:

NLS table for utf8 is broken and cannot be fixed.

So instead of broken utf8 nls functions char2uni() and uni2char() use
functions utf8_to_utf32() and utf32_to_utf8() which implements correct
encoding and decoding between Unicode code points and UTF-8 sequence.

When iochatset=utf8 is used then set hsb->nls_io to NULL and use it for
distinguish between the fact if NLS table or native UTF-8 functions should
be used.

Signed-off-by: Pali Rohár <pali@kernel.org>
---
fs/hfs/super.c | 33 ++++++++++++++++++++++-----------
fs/hfs/trans.c | 24 ++++++++++++++++++++----
2 files changed, 42 insertions(+), 15 deletions(-)

diff --git a/fs/hfs/super.c b/fs/hfs/super.c
index 86bc46746c7f..076308df41cf 100644
--- a/fs/hfs/super.c
+++ b/fs/hfs/super.c

@@ -149,10 +149,13 @@ static int hfs_show_options(struct seq_file *seq, struct dentry *root)

		seq_printf(seq, ",part=%u", sbi->part);
	if (sbi->session >= 0)
		seq_printf(seq, ",session=%u", sbi->session);
-	if (sbi->nls_disk)
+	if (sbi->nls_disk) {
		seq_printf(seq, ",codepage=%s", sbi->nls_disk->charset);

-	if (sbi->nls_io)
-		seq_printf(seq, ",iocharset=%s", sbi->nls_io->charset);
+		if (sbi->nls_io)
+			seq_printf(seq, ",iocharset=%s", sbi->nls_io->charset);
+		else
+			seq_puts(seq, ",iocharset=utf8");
+	}
	if (sbi->s_quiet)
		seq_printf(seq, ",quiet");
	return 0;

@@ -225,6 +228,7 @@ static int parse_options(char *options, struct hfs_sb_info *hsb)

	char *p;
	substring_t args[MAX_OPT_ARGS];
	int tmp, token;
+	int have_iocharset;

	/* initialize the sb with defaults */
	hsb->s_uid = current_uid();

@@ -239,6 +243,8 @@ static int parse_options(char *options, struct hfs_sb_info *hsb)

	if (!options)
		return 1;

+	have_iocharset = 0;

+
	while ((p = strsep(&options, ",")) != NULL) {
		if (!*p)
			continue;

@@ -332,18 +338,22 @@ static int parse_options(char *options, struct hfs_sb_info *hsb)

			kfree(p);
			break;
		case opt_iocharset:
-			if (hsb->nls_io) {
+			if (have_iocharset) {
				pr_err("unable to change iocharset\n");
				return 0;
			}
			p = match_strdup(&args[0]);
-			if (p)
-				hsb->nls_io = load_nls(p);
-			if (!hsb->nls_io) {
-				pr_err("unable to load iocharset \"%s\"\n", p);
-				kfree(p);
+			if (!p)
				return 0;
+			if (strcmp(p, "utf8") != 0) {
+				hsb->nls_io = load_nls(p);
+				if (!hsb->nls_io) {
+					pr_err("unable to load iocharset \"%s\"\n", p);
+					kfree(p);
+					return 0;
+				}
			}
+			have_iocharset = 1;

			kfree(p);
			break;
		default:

@@ -351,7 +361,7 @@ static int parse_options(char *options, struct hfs_sb_info *hsb)

		}
	}

-	if (hsb->nls_io && !hsb->nls_disk) {
+	if (have_iocharset && !hsb->nls_disk) {
		/*
		 * Previous version of hfs driver did something unexpected:
		 * When codepage was not defined but iocharset was then

@@ -382,7 +392,8 @@ static int parse_options(char *options, struct hfs_sb_info *hsb)

			return 0;
		}
	}
-	if (hsb->nls_disk && !hsb->nls_io) {
+	if (hsb->nls_disk &&
+	    !have_iocharset && strcmp(CONFIG_NLS_DEFAULT, "utf8") != 0) {

		hsb->nls_io = load_nls_default();
		if (!hsb->nls_io) {
			pr_err("unable to load default iocharset\n");

diff --git a/fs/hfs/trans.c b/fs/hfs/trans.c
index c75682c61b06..bff8e54003ab 100644
--- a/fs/hfs/trans.c
+++ b/fs/hfs/trans.c

@@ -44,7 +44,7 @@ int hfs_mac2asc(struct super_block *sb, char *out, const struct hfs_name *in)

		srclen = HFS_NAMELEN;
	dst = out;
	dstlen = HFS_MAX_NAMELEN;
-	if (nls_io) {
+	if (nls_disk) {
		wchar_t ch;

		while (srclen > 0) {

@@ -57,7 +57,12 @@ int hfs_mac2asc(struct super_block *sb, char *out, const struct hfs_name *in)

			srclen -= size;
			if (ch == '/')
				ch = ':';
-			size = nls_io->uni2char(ch, dst, dstlen);
+			if (nls_io)
+				size = nls_io->uni2char(ch, dst, dstlen);
+			else if (dstlen > 0)
+				size = utf32_to_utf8(ch, dst, dstlen);
+			else
+				size = -ENAMETOOLONG;
			if (size < 0) {
				if (size == -ENAMETOOLONG)
					goto out;

@@ -101,11 +106,22 @@ void hfs_asc2mac(struct super_block *sb, struct hfs_name *out, const struct qstr

	srclen = in->len;
	dst = out->name;
	dstlen = HFS_NAMELEN;
-	if (nls_io) {
+	if (nls_disk) {
		wchar_t ch;
+		unicode_t u;

		while (srclen > 0) {
-			size = nls_io->char2uni(src, srclen, &ch);
+			if (nls_io)
+				size = nls_io->char2uni(src, srclen, &ch);
+			else {
+				size = utf8_to_utf32(str, strlen, &u);
+				if (size >= 0) {
+					if (u <= MAX_WCHAR_T)
+						ch = u;
+					else
+						size = -EINVAL;
+				}
+			}
			if (size < 0) {
				ch = '?';
				size = 1;
-- 
2.20.1