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 16E634432 for ; Mon, 11 Sep 2023 14:10:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 86B88C433C9; Mon, 11 Sep 2023 14:10:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1694441419; bh=S0iqzVFt9mWY8/4Hx8NMfT5iDw9NGELxRCxcBolGnQs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=yuImTUfEutZuHoN7a1kB+FPQKPoO5b2CVbUVfRukCX200q1t0jFh5S3em8eigMlmI bElri1L7/vXVBJzyy41Mp0yV01pUuVbd2q3lH9lD/cb6Ro/Ko5HBTohrot66ol/hAB WZ/tyxzfzpYqil51L+M8cIXFksAdXMQIm0OlE7Bk= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Alex Williamson , Dmitry Torokhov , Kevin Tian , Sasha Levin Subject: [PATCH 6.5 399/739] kvm/vfio: ensure kvg instance stays around in kvm_vfio_group_add() Date: Mon, 11 Sep 2023 15:43:18 +0200 Message-ID: <20230911134702.327419651@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20230911134650.921299741@linuxfoundation.org> References: <20230911134650.921299741@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.5-stable review patch. If anyone has any objections, please let me know. ------------------ From: Dmitry Torokhov [ Upstream commit 9e0f4f2918c2ff145d3dedee862d9919a6ed5812 ] kvm_vfio_group_add() creates kvg instance, links it to kv->group_list, and calls kvm_vfio_file_set_kvm() with kvg->file as an argument after dropping kv->lock. If we race group addition and deletion calls, kvg instance may get freed by the time we get around to calling kvm_vfio_file_set_kvm(). Previous iterations of the code did not reference kvg->file outside of the critical section, but used a temporary variable. Still, they had similar problem of the file reference being owned by kvg structure and potential for kvm_vfio_group_del() dropping it before kvm_vfio_group_add() had a chance to complete. Fix this by moving call to kvm_vfio_file_set_kvm() under the protection of kv->lock. We already call it while holding the same lock when vfio group is being deleted, so it should be safe here as well. Fixes: 2fc1bec15883 ("kvm: set/clear kvm to/from vfio_group when group add/delete") Reviewed-by: Alex Williamson Signed-off-by: Dmitry Torokhov Reviewed-by: Kevin Tian Link: https://lore.kernel.org/r/20230714224538.404793-1-dmitry.torokhov@gmail.com Signed-off-by: Alex Williamson Signed-off-by: Sasha Levin --- virt/kvm/vfio.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c index af3d0cf06e4c6..365d30779768a 100644 --- a/virt/kvm/vfio.c +++ b/virt/kvm/vfio.c @@ -180,10 +180,10 @@ static int kvm_vfio_file_add(struct kvm_device *dev, unsigned int fd) list_add_tail(&kvf->node, &kv->file_list); kvm_arch_start_assignment(dev->kvm); + kvm_vfio_file_set_kvm(kvf->file, dev->kvm); mutex_unlock(&kv->lock); - kvm_vfio_file_set_kvm(kvf->file, dev->kvm); kvm_vfio_update_coherency(dev); return 0; -- 2.40.1