From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A165148640F for ; Fri, 25 Sep 2026 10:30:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790332250; cv=none; b=TPTOzI8buWBrkuoV+zReWSyFeJbebffmup1djW/PTktP8DIQtvY+EpKKuTIuCUJq8t7bIIhvEqOiERpZB7dC2dqTLD6rBjhzdidzBwnxLTo/kb5pXqfEJnRFxeHlLg8jcZFWzgZT4JhO+mLtH0CJ9+zie7mXDSqXYYM0IBsA9xI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790332250; c=relaxed/simple; bh=jUbuxj6bG2rsYCd4ABObm80lAdDETEF7ijglVTfaRsk=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=MWHvhwxrNUhyTPqWmUfxcKuBkdzgailCggLyR+Qm0B9Zr5mcxUTNnK5T0zTIhHnpAktR7MhYJRP3kWkGBorpWbW6B3yHxJsSatJTnuDBaSBc+xISfwi3XlGyV/eEILVnA28vLnTfvBRjQ7kSpZKkj2IhcnkUgDlFCt/ssO17DGs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=QcOEP5+9; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="QcOEP5+9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 09A821F000FF; Fri, 25 Sep 2026 10:30:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790332249; bh=BS+A7VLJpqVj+VrSkszOgsg2opdWq6VW2nVIJPTZgYE=; h=From:To:Cc:Subject:Date:Reply-To; b=QcOEP5+9LHBEj36eNxSKugUY9TuQatlcXSSJREsLGl6K3FlgXD6oSyCm8FGltS4SJ H+1FuASmtDOzGs8LDqd+mNZ2iCO/XBdXBBgb+DokrzUTepbFkpuqqLNsXi+8ERbmmF iO0y580pmdu2F2nmyzSi6mx962KIXAZ7lEUXXxts= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-97944: x86/cfi: Fix FineIBT hash offset in cfi_get_func_hash() Date: Fri, 25 Sep 2026 12:24:07 +0200 Message-ID: <2026092512-CVE-2026-97944-e075@gregkh> X-Mailer: git-send-email 2.55.0 Reply-To: , Precedence: bulk X-Mailing-List: linux-cve-announce@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3249; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=1+35xmAD/kCrlxfbejZBdDUtPr4zLpkp7vSblUoIAxE=; b=owGbwMvMwCRo6H6F97bub03G02pJDFnbvEPWL2PzvaSVoDKzevrm1qj7SsuvP+f86HAznWvyv S9cws97O2JZGASZGGTFFFm+bOM5ur/ikKKXoe1pmDmsTCBDGLg4BWAiQlEM87NK9yR9a2BRtH/z VGN1+fS5PL7/nzIsmP97UkxpTeTFgyd/rZpRZj5D+lzcbwA= X-Developer-Key: i=gregkh@linuxfoundation.org; a=openpgp; fpr=F4B60CC5BF78C2214A313DCB3147D40DDB2DFB29 Content-Transfer-Encoding: 8bit From: Greg Kroah-Hartman Description =========== In the Linux kernel, the following vulnerability has been resolved: x86/cfi: Fix FineIBT hash offset in cfi_get_func_hash() The switch of the FineIBT preamble from "subl $hash, %r10d" to the shorter "subl $hash, %eax" moved the hash immediate from offset 7 to offset 5 of the preamble. fineibt_preamble_hash was updated to match, but the open-coded offset in cfi_get_func_hash() was missed and it still reads the hash at offset 7. cfi_get_func_hash() is used by the BPF JIT to give a struct_ops trampoline the CFI hash of the stub function it stands in for. With FineIBT the trampoline now gets the upper half of the real hash followed by the first two bytes of the next instruction, so the first indirect call from the kernel into a struct_ops program, tcp_init_congestion_control() calling ->init() of a BPF congestion control for example, fails the FineIBT check and the kernel dies with a CFI failure. Move the FineIBT preamble template and its offset defines above cfi_get_func_hash() and use fineibt_preamble_hash there, so every reader of the preamble shares one definition of its layout. The CFI_FINEIBT arm is only built with CONFIG_FINEIBT, the only configuration in which cfi_mode can take that value. cfi_get_func_arity() does not need the same treatment: the __bhi_args call whose displacement it reads still ends at the function address. The Linux kernel CVE team has assigned CVE-2026-97944 to this issue. Affected and fixed versions =========================== Issue introduced in 6.18 with commit 85a2d4a890dce3cfc9c14aa91afc3dd7af8e3bf5 and fixed in 6.18.53 with commit cd9b4595d6283f9b8a35d7ae607508de45a351ce Issue introduced in 6.18 with commit 85a2d4a890dce3cfc9c14aa91afc3dd7af8e3bf5 and fixed in 7.2.7 with commit 67cf94c30a8b5ebc839f282f5c5a522b35903524 Issue introduced in 6.18 with commit 85a2d4a890dce3cfc9c14aa91afc3dd7af8e3bf5 and fixed in 7.3-rc4 with commit 5a5d26f2cfe13467166219f6bf58099326912ddb 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-2026-97944 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: arch/x86/kernel/alternative.c 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/cd9b4595d6283f9b8a35d7ae607508de45a351ce https://git.kernel.org/stable/c/67cf94c30a8b5ebc839f282f5c5a522b35903524 https://git.kernel.org/stable/c/5a5d26f2cfe13467166219f6bf58099326912ddb