[PATCH] efi_loader: Fix buffer underflow If the array index 'i' < 128, the 'codepage' array is accessed using [-128...-1] in efi_unicode_collation.c:262. This can lead to a buffer overflow. Negative index in efi_unicode_collation.c:262. The index of the 'codepage' array should be c-0x80 instead of i-0x80.

[Heinrich Schuchardt]

On 11/22/22 08:33, Mikhail Ilin wrote:
> Fixes: 0bc4b0da7b59 ("efi_loader: EFI_UNICODE_COLLATION_PROTOCOL")

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Otherwise:
Reviewed-by: Heinrich Schuchardt <xypron.glpk at gmx.de>

> Signed-off-by: Mikhail Ilin <ilin.mikhail.ol at gmail.com>
> ---
>   lib/efi_loader/efi_unicode_collation.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/lib/efi_loader/efi_unicode_collation.c b/lib/efi_loader/efi_unicode_collation.c
> index c700be8756..282045b556 100644
> --- a/lib/efi_loader/efi_unicode_collation.c
> +++ b/lib/efi_loader/efi_unicode_collation.c
> @@ -259,7 +259,7 @@ static void EFIAPI efi_fat_to_str(struct efi_unicode_collation_protocol *this,
>   	for (i = 0; i < fat_size; ++i) {
>   		c = (unsigned char)fat[i];
>   		if (c > 0x80)
> -			c = codepage[i - 0x80];
> +			c = codepage[c - 0x80];
>   		string[i] = c;
>   		if (!c)
>   			break;