linux-cve-announce - CVE-2025-37984: crypto: ecdsa - Harden against integer overflows in DIV_ROUND

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Message-ID: <2025052037-CVE-2025-37984-be4c@gregkh>
Date: Tue, 20 May 2025 19:07:37 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-37984: crypto: ecdsa - Harden against integer overflows in DIV_ROUND_UP()

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

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().

The Linux kernel CVE team has assigned CVE-2025-37984 to this issue.

Affected and fixed versions
===========================

	Fixed in 6.14.5 with commit 921b8167f10708e38080f84e195cdc68a7a561f1
	Fixed in 6.15-rc1 with commit b16510a530d1e6ab9683f04f8fb34f2e0f538275

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2025-37984
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	crypto/ecc.c
	crypto/ecdsa-p1363.c
	crypto/ecdsa-x962.c
	include/linux/math.h

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/921b8167f10708e38080f84e195cdc68a7a561f1
	https://git.kernel.org/stable/c/b16510a530d1e6ab9683f04f8fb34f2e0f538275