From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794366365; b=q4grrw0rLkw1T8qyhf1/PnSiczfCD3yQHoR/N/VKXSCRVAXTkEqTUa1BWLBpYmX49uLV U+B/nM68tvCUTsiN2TQnZO6XoRUz/tcu8oTgHMhHp5ZpnfSxxkpsQKR1XS3MmOeFkSF11 LGCpyyVlng5sSAt7wkCDAmAYcBuhxQxCHB92qJ+ifrRO6lTZP7XVlZkfY5GgctF4KeGdO sb9bWUHRZ8h1f1kcUENtturICg8xr0WXqW0Q9Vc6EusvN7KMXv/reLYktxqDI+qAs2Wx6 ltv1P21VWNx/rr7ULgqDy2ZLUawjuMnFGI2a+pEEaxGX74PMsyotNLHNlXnTubR9GqQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794366365; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=ZhK6fxGp0Yhji3Lq0mMK6EbuS1F4rWHrpBGbgJUnycM=; b=xbNfmd6S7JCWaTHZsyawccwSjoToowfJRLEF+7RXKJnM35cc3M4XY9/LisMD+sZaq4xM TQUZoSUdxfgEVQaHIMuR87anrK4g/XG2K1LT3eQedTayp5LvibLaS52o4sqMC0Lqd0wlk //sINgCDEfCkONZUlT9IARpMXE406UZJUVKfqRzrVVTvjUJuB9+WhjHitDUUmf4FLSkBK seHOyqzaLq4K0FKeQO28hik4oO6bG0av4Ug1GZKlqEj0Ol9ZOPsZqQElfKsTyQCnG4kjq nIeKl+Q1HoQ5EpG5QGVpZzJFwjATidzJDuwCGLzWN70T+hDfHFXMWspA89o76grLEfg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=EfrDZg9p; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D0983606A320 for ; Wed, 11 Nov 2026 03:06:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=EfrDZg9p Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0CF4C1F0089F; Wed, 11 Nov 2026 03:06:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794366365; bh=ZhK6fxGp0Yhji3Lq0mMK6EbuS1F4rWHrpBGbgJUnycM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=EfrDZg9paVFizpE2hATnU/gqxVVIJ9aqqPFm2PdU5uWMWVUo+5eQoNksbuE2Yh+Dl NKm9iISHXbaIyb1JTjoSrlX8t/M7O3ZCata0nWfJMiW+wfYcOhCRbgmuGh6+2WNKjY wDbx8YgxV6fBlaerX6HS3Uip5oDH9TXxZSVaan36GO1dTY4KfjdbWN7awzjByL1SCc OKetMQ7Ee4SMrOB/xLgTpZkdyIsMCz71kbAdqi0U5cBW5FZgHyq18yYZUpvnJrNOh2 PBQBjEnamDv/186jayt8bXiiZaM0IU4ZoV5tYi80lHDox4zT8dkuG8WYmptcKu4Ebi R3/fiGPc2aZDg== From: Sasha Levin To: stable@vger.kernel.org Cc: David Woodhouse , sashiko-bot@kernel.org, Paul Durrant , Paolo Bonzini , Sasha Levin Subject: [PATCH 5.15.y] KVM: x86/xen: Enforce 4-byte alignment of vcpu_info registration Date: Tue, 10 Nov 2026 22:06:03 -0500 Message-ID: <20261111030546.811623-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261107055744-failed-5.15-eacdb76c5f04@kernel.org> References: <20261107055744-failed-5.15-eacdb76c5f04@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: David Woodhouse [ Upstream commit eacdb76c5f04956035c5d7f7e1973028f30684a2 ] Xen's map_guest_area() enforces that vcpu_info is aligned to sizeof(xen_ulong_t). KVM has no such check, allowing a guest to register vcpu_info at an arbitrary byte alignment. Enforce unconditional 4-byte alignment regardless of the current shinfo mode. This is sufficient because subsequent commits ensure that all locked atomic operations on vcpu_info fields use at most 32-bit accesses. Return -ENXIO on failure, matching Xen's map_guest_area() behaviour for unaligned requests. Originally observed in review of an unrelated patch: https://lore.kernel.org/all/20260604193554.1BA311F00893@smtp.kernel.org/ Cc: stable@vger.kernel.org Fixes: 73e69a86347a ("KVM: x86/xen: register vcpu info") Reported-by: sashiko-bot@kernel.org Closes: https://lore.kernel.org/all/20260604193554.1BA311F00893@smtp.kernel.org Assisted-by: Kiro:claude-opus-4.6-1m Signed-off-by: David Woodhouse Reviewed-by: Paul Durrant Link: https://patch.msgid.link/20260831213632.81023-7-dwmw2@infradead.org Signed-off-by: Paolo Bonzini [ sashal: Omitted the HVA alignment check because only GPA registration is supported. ] Signed-off-by: Sasha Levin --- arch/x86/kvm/xen.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c index ab9f88de6deb9..69c2d8dda2d25 100644 --- a/arch/x86/kvm/xen.c +++ b/arch/x86/kvm/xen.c @@ -356,6 +356,10 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data) break; } + r = -ENXIO; + if (!IS_ALIGNED(data->u.gpa, sizeof(u32))) + break; + /* It must fit within a single page */ if ((data->u.gpa & ~PAGE_MASK) + sizeof(struct vcpu_info) > PAGE_SIZE) { r = -EINVAL; -- 2.53.0