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=1794049066; b=Cj55VlibnBVbTUS+gJaTw6KnedR8jAKcafH2uVL9l3kikU21q+GQlDUSD8H3AokU2ioN mJezNUvrIr+8GH+qZAqgIGA6Sy+p1mj/NLJvrcrBBQWOhh3H3ys8esA/MuOLRx0d6TeSh rCGjYwRS0xDv92jAriAYjCWpSn69XlAjwE4WCtmOjf40NG5wCAqHVL4tdGFtDYtSzAnGL ZILACgXe5hoYOkJNh3YltEuWXFEis7bGLHKk9Syil+tnff1bqiBqjkuGIhv1vvzXU/A+Q MDe9AXIRe0zBy1P0rvTJRGpkGSmVZh5p8yL0uuAz0wX+5FSM00G1FPon5KNAeNDWYlg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794049066; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=ajFRbX3CHCgeSBd6QCzKDDk8zTL/dAdkftlR6QAH5s4=; b=sjAnW9uY0yywkSjPFVxylFzP0lrHh8Rtxi6TF6Pk9lGXzJisHASA48h9AZw4AnRJYJ4I OqLSYrQP/93ChMmDe9FsqfyVFJ7nk9RgkNgA86ezYC+feKos2N8gxIW/ComTkLvD3Acge wLyLXNev0nH+8F/NtuyD3fIh/peJgjx3aF0otWZuINlSw0JoBl24J4+Fpu79JxehUehnH /JGKpOz3Ekg3A4WoCyxaK/dZJdMxXGT0RpU7xsLWv+8cOtXXM93eF1yvS/YGR9ZfTujaX jme8lj03A0EPni2KGTVr6075MpT30o2J//SI1jCV12keFcALxm9pFIfp5sjWooEZt+w== 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=CZC5bZYA; 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 26B36606A326 for ; Sat, 7 Nov 2026 10:57:46 +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=CZC5bZYA Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6D1111F008A2; Sat, 7 Nov 2026 10:57:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794049066; bh=ajFRbX3CHCgeSBd6QCzKDDk8zTL/dAdkftlR6QAH5s4=; h=From:To:Cc:Subject:Date; b=CZC5bZYAxmFp7YqWOmn8AzizczEyneVersLYi/01yAn+0dkcnXVQreStLTajNbI70 eb6Ree+YUJIXx7s1rWRkGGjbh7tKHttmAyv20FGfeMZFuJUVD3Pr3Czmcl8LEOIU97 TVn8oQuGsEIZXvsFX2qsHrJUTJla1UNZsTQ/08gxENVrSkJ37dEOXlRANcBBkVeUMd gixEEQVgqOGRXi7ZjZ8dQMT8m5B1RraG3BiuRFDy8ZU9k66lCid8p+oXYI8x7YonCB EufM9ofo5uJVJ+90yoUlp4FzfANprmC0wPKnz/TDJBjOa+XAnIuAV5CNyW26ZJC2C7 IyRqRCWG7IkKg== From: Sasha Levin To: dwmw@amazon.co.uk, sashiko-bot@kernel.org, paul@xen.org, pbonzini@redhat.com Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] KVM: x86/xen: Enforce 4-byte alignment of vcpu_info registration" failed to apply to 5.15-stable tree Date: Sat, 7 Nov 2026 05:57:44 -0500 Message-ID: <20261107055744-failed-5.15-eacdb76c5f04@kernel.org> X-Mailer: git-send-email 2.53.0 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-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x eacdb76c5f04956035c5d7f7e1973028f30684a2 # git commit -s git send-email --to '' --in-reply-to '20261107055744-failed-5.15-eacdb76c5f04@kernel.org' --subject-prefix 'PATCH 5.15.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From eacdb76c5f04956035c5d7f7e1973028f30684a2 Mon Sep 17 00:00:00 2001 From: David Woodhouse Date: Mon, 31 Aug 2026 22:26:37 +0100 Subject: [PATCH] KVM: x86/xen: Enforce 4-byte alignment of vcpu_info registration 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 --- arch/x86/kvm/xen.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c index d0bdc6e8eb28c..15c508b7b28b7 100644 --- a/arch/x86/kvm/xen.c +++ b/arch/x86/kvm/xen.c @@ -941,6 +941,10 @@ 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; + r = kvm_gpc_activate(&vcpu->arch.xen.vcpu_info_cache, data->u.gpa, sizeof(struct vcpu_info)); } else { @@ -950,6 +954,10 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data) break; } + r = -ENXIO; + if (!IS_ALIGNED(data->u.hva, sizeof(u32))) + break; + r = kvm_gpc_activate_hva(&vcpu->arch.xen.vcpu_info_cache, data->u.hva, sizeof(struct vcpu_info)); } -- 2.53.0