From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 2457B7C6EB; Mon, 8 Apr 2024 13:16:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712582206; cv=none; b=FtSzJYTO92NYn/vFf+arhM+LsVkfyOehpF/UdKJls35hTzPrF/PCM/u04bY0qlnr/cNB0HKRPkH78+x8BlhXZnA1r748nfu0FMdjSJ6BHuJ8onyUTCDbZpzw5ruI29sIfoZnMxAmU6Ii2530gbd9PQMemVvoWOXiMm8MjPXCMIU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712582206; c=relaxed/simple; bh=qRTJ9+6rTbsAU3hdunc36l0yPNe2IKfR5AQz6C68y+c=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=htELbeWOkUI+sETFLObAVDsH2pMaLqnBiob+aJMPOTl5RsKy1uEioyC5hV/lJnvwCUDI2O1dGVLl1Dx4YjAgWFVDl4pH1Qu/T+Mdv8FEO988leC8tqs/VCTjykiKPKvqqOfJT53ryXbhYQAOz1zeAvat51P78toi49N0vGUJqjs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Lvr8uuDd; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Lvr8uuDd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9CACDC433F1; Mon, 8 Apr 2024 13:16:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1712582206; bh=qRTJ9+6rTbsAU3hdunc36l0yPNe2IKfR5AQz6C68y+c=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Lvr8uuDd4U+NzwvTRZtBxFWS9MTxwM0HyOf/5LeI0v+lYKWHjXodmh6tnRQDetCmJ JFczl5oAKI8OIY0jUU4v/ZEmlmrFZ/iqB4EueUVOHQQbnH/yGE+oS10EcvRrDcKThw v+v63n6tEYKhsrAmgqfXUdwTnIoC6IDMg2CVUlic= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Gabe Kirkpatrick , Josh Eads , Peter Gonda , Sean Christopherson , Paolo Bonzini Subject: [PATCH 5.15 123/690] KVM: SVM: Flush pages under kvm->lock to fix UAF in svm_register_enc_region() Date: Mon, 8 Apr 2024 14:49:49 +0200 Message-ID: <20240408125404.015070012@linuxfoundation.org> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240408125359.506372836@linuxfoundation.org> References: <20240408125359.506372836@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Sean Christopherson commit 5ef1d8c1ddbf696e47b226e11888eaf8d9e8e807 upstream. Do the cache flush of converted pages in svm_register_enc_region() before dropping kvm->lock to fix use-after-free issues where region and/or its array of pages could be freed by a different task, e.g. if userspace has __unregister_enc_region_locked() already queued up for the region. Note, the "obvious" alternative of using local variables doesn't fully resolve the bug, as region->pages is also dynamically allocated. I.e. the region structure itself would be fine, but region->pages could be freed. Flushing multiple pages under kvm->lock is unfortunate, but the entire flow is a rare slow path, and the manual flush is only needed on CPUs that lack coherency for encrypted memory. Fixes: 19a23da53932 ("Fix unsynchronized access to sev members through svm_register_enc_region") Reported-by: Gabe Kirkpatrick Cc: Josh Eads Cc: Peter Gonda Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson Message-Id: <20240217013430.2079561-1-seanjc@google.com> Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/svm/sev.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -1662,20 +1662,22 @@ int svm_register_enc_region(struct kvm * goto e_free; } - region->uaddr = range->addr; - region->size = range->size; - - list_add_tail(®ion->list, &sev->regions_list); - mutex_unlock(&kvm->lock); - /* * The guest may change the memory encryption attribute from C=0 -> C=1 * or vice versa for this memory range. Lets make sure caches are * flushed to ensure that guest data gets written into memory with - * correct C-bit. + * correct C-bit. Note, this must be done before dropping kvm->lock, + * as region and its array of pages can be freed by a different task + * once kvm->lock is released. */ sev_clflush_pages(region->pages, region->npages); + region->uaddr = range->addr; + region->size = range->size; + + list_add_tail(®ion->list, &sev->regions_list); + mutex_unlock(&kvm->lock); + return ret; e_free: