On Tue, Dec 12, 2023 at 04:13:20PM +0100, Roman Žilka wrote:
> vc_translate_unicode() and vc_sanitize_unicode() parse input to the
> UTF-8-enabled console, marking invalid byte sequences and producing Unicode
> codepoints. The current algorithm follows ancient Unicode and may accept invalid
> byte sequences, pass on non-existent codepoints and reject valid sequences.
>
> The patch restores the functions' compliance with modern Unicode (v15.1 + many
> previous versions) as well as RFC 3629.
> 1. Codepoint space is limited to 0x10FFFF.
> 2. "Noncharacters", such as U+FFFE, U+FFFF, are no longer invalid in Unicode and
> will be accepted. Another option was to complete the set of noncharacters
> (used to be just those two, now there's more) and preserve the rejection
> step. This is indeed what Unicode suggests (v15.1, chap. 23.7) (not
> requires), but most codepoints are !iswprint(), so selecting just the
> noncharacters seemed arbitrary and futile (and unnecessary).
>
> On the side:
> 3. What remained of vc_sanitize_unicode() is in vc_translate_unicode().
> 4. Corrected vc_translate_unicode() doc (@rescan).
>
> This is not a security patch. I'm not aware of any present security implications
> of the old code.
>
> Signed-off-by: Roman Žilka <roman.zilka@xxxxxxxxx>
> ---
> drivers/tty/vt/vt.c | 36 +++++++-----------------------------
> 1 file changed, 7 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
> index 156efda7c80d..215e162ec8af 100644
> --- a/drivers/tty/vt/vt.c
> +++ b/drivers/tty/vt/vt.c
> @@ -2587,23 +2587,11 @@ static inline int vc_translate_ascii(const struct vc_data *vc, int c)
> }
>
>
> -/**
> - * vc_sanitize_unicode - Replace invalid Unicode code points with U+FFFD
> - * @c: the received character, or U+FFFD for invalid sequences.
> - */
> -static inline int vc_sanitize_unicode(const int c)
> -{
> - if ((c >= 0xd800 && c <= 0xdfff) || c == 0xfffe || c == 0xffff)
> - return 0xfffd;
> -
> - return c;
> -}
> -
> /**
> * vc_translate_unicode - Combine UTF-8 into Unicode in @vc_utf_char
> * @vc: virtual console
> - * @c: character to translate
> - * @rescan: we return true if we need more (continuation) data
> + * @c: UTF-8 byte to translate
> + * @rescan: true => @c wasn't translated here and needs to be re-processed
> *
> * @vc_utf_char is the being-constructed unicode character.
> * @vc_utf_count is the number of continuation bytes still expected to arrive.
> @@ -2611,10 +2599,7 @@ static inline int vc_sanitize_unicode(const int c)
> */
> static int vc_translate_unicode(struct vc_data *vc, int c, bool *rescan)
> {
> - static const u32 utf8_length_changes[] = {
> - 0x0000007f, 0x000007ff, 0x0000ffff,
> - 0x001fffff, 0x03ffffff, 0x7fffffff
> - };
> + static const u32 utf8_length_changes[] = {0x7f, 0x7ff, 0xffff, 0x10ffff};
>
> /* Continuation byte received */
> if ((c & 0xc0) == 0x80) {
> @@ -2629,12 +2614,12 @@ static int vc_translate_unicode(struct vc_data *vc, int c, bool *rescan)
>
> /* Got a whole character */
> c = vc->vc_utf_char;
> - /* Reject overlong sequences */
> + /* Reject overlong sequences and surrogates */
> if (c <= utf8_length_changes[vc->vc_npar - 1] ||
> - c > utf8_length_changes[vc->vc_npar])
> + c > utf8_length_changes[vc->vc_npar] ||
> + (c & 0xfff800) == 0x00d800)
> return 0xfffd;
> -
> - return vc_sanitize_unicode(c);
> + return c;
> }
>
> /* Single ASCII byte or first byte of a sequence received */
> @@ -2660,14 +2645,7 @@ static int vc_translate_unicode(struct vc_data *vc, int c, bool *rescan)
> } else if ((c & 0xf8) == 0xf0) {
> vc->vc_utf_count = 3;
> vc->vc_utf_char = (c & 0x07);
> - } else if ((c & 0xfc) == 0xf8) {
> - vc->vc_utf_count = 4;
> - vc->vc_utf_char = (c & 0x03);
> - } else if ((c & 0xfe) == 0xfc) {
> - vc->vc_utf_count = 5;
> - vc->vc_utf_char = (c & 0x01);
> } else {
> - /* 254 and 255 are invalid */
> return 0xfffd;
> }
>
>
> base-commit: a39b6ac3781d46ba18193c9dbb2110f31e9bffe9
> --
> 2.41.0
>
>
Hi,
This is the friendly patch-bot of Greg Kroah-Hartman. You have sent him
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Please read the section entitled "The canonical patch format" in the
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