On Thu, 27 Mar 2025 23:34:29 +0100 Ben Hutchings ben@decadent.org.uk wrote:
On Wed, 2025-03-05 at 10:21 +0800, Ming Lei wrote:
From: Olivier Gayot olivier.gayot@canonical.com
The utf16_le_to_7bit function claims to, naively, convert a UTF-16 string to a 7-bit ASCII string. By naively, we mean that it:
- drops the first byte of every character in the original UTF-16 string
- checks if all characters are printable, and otherwise replaces them by exclamation mark "!".
This means that theoretically, all characters outside the 7-bit ASCII range should be replaced by another character. Examples:
- lower-case alpha (ɒ) 0x0252 becomes 0x52 (R)
- ligature OE (œ) 0x0153 becomes 0x53 (S)
- hangul letter pieup (ㅂ) 0x3142 becomes 0x42 (B)
- upper-case gamma (Ɣ) 0x0194 becomes 0x94 (not printable) so gets replaced by "!"
Also any character with low 8 bits equal to 0 terminates the string.
The result of this conversion for the GPT partition name is passed to user-space as PARTNAME via udev, which is confusing and feels questionable.
Indeed. But this change seems to make it worse!
[...]
This results in many values which should be replaced by "!" to be kept as-is, despite not being valid 7-bit ASCII. Examples:
e with acute accent (é) 0x00E9 becomes 0xE9 - kept as-is because isprint(0xE9) returns 1.
euro sign (€) 0x20AC becomes 0xAC - kept as-is because isprint(0xAC) returns 1.
[...]
--- a/block/partitions/efi.c +++ b/block/partitions/efi.c @@ -682,7 +682,7 @@ static void utf16_le_to_7bit(const __le16 *in, unsigned int size, u8 *out) out[size] = 0; while (i < size) {
u8 c = le16_to_cpu(in[i]) & 0xff;
u8 c = le16_to_cpu(in[i]) & 0x7f;if (c && !isprint(c)) c = '!';
Now we map 'é' to 'i' and '€' to ','. Didn't we want to map them to '!'?
We shouldn't mask the input character; instead we should do a range check before calling isprint(). Something like:
u16 uc = le16_to_cpu(in[i]); u8 c;
if (uc < 0x80 && (uc == 0 || isprint(uc)))
Given that, for 7-bit ascii, isprint(uc) is equivalent to (uc >= 0x20 && uc <= 0x7e) you can do: if (uc >= 0x20 && uc <= 0x7e) c = uc; else c = uc ? '!' : 0;
David
c = uc;else c = '!';
Ben.