Early Access — Mondoo Vulnerability Intelligence is currently in preview.
In the Linux kernel, the following vulnerability has been resolved:
crypto: ecdsa - Harden against integer overflows in DIV_ROUND_UP()
Herbert notes that DIV_ROUND_UP() may overflow unnecessarily if an ecdsa implementation's ->key_size() callback returns an unusually large value. Herbert instead suggests (for a division by 8):
X / 8 + !!(X & 7)
Based on this formula, introduce a generic DIV_ROUND_UP_POW2() macro and use it in lieu of DIV_ROUND_UP() for ->key_size() return values.
Additionally, use the macro in ecc_digits_from_bytes(), whose "nbytes" parameter is a ->key_size() return value in some instances, or a user-specified ASN.1 length in the case of ecdsa_get_signature_rs().