From: Olivier Gayot <olivier.gayot@xxxxxxxxxxxxx> commit e06472bab2a5393430cc2fbc3211cd3602422c1e upstream. 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 "!" 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. However, there is a flaw in the conversion function itself. By dropping one byte of each character and using isprint() to check if the remaining byte corresponds to a printable character, we do not actually guarantee that the resulting character is 7-bit ASCII. This happens because we pass 8-bit characters to isprint(), which in the kernel returns 1 for many values > 0x7f - as defined in ctype.c. 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. This way has broken pyudev utility[1], fixes it by using a mask of 7 bits instead of 8 bits before calling isprint. Link: https://github.com/pyudev/pyudev/issues/490#issuecomment-2685794648 [1] Link: https://lore.kernel.org/linux-block/4cac90c2-e414-4ebb-ae62-2a4589d9dc6e@xxxxxxxxxxxxx/ Cc: Mulhern <amulhern@xxxxxxxxxx> Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Olivier Gayot <olivier.gayot@xxxxxxxxxxxxx> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> Link: https://lore.kernel.org/r/20250305022154.3903128-1-ming.lei@xxxxxxxxxx Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- block/partitions/efi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/block/partitions/efi.c +++ b/block/partitions/efi.c @@ -672,7 +672,7 @@ static void utf16_le_to_7bit(const __le1 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 = '!'; Patches currently in stable-queue which might be from olivier.gayot@xxxxxxxxxxxxx are queue-5.10/block-fix-conversion-of-gpt-partition-name-to-7-bit.patch
