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 640C731D730; Mon, 5 Oct 2026 19:06:01 +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=1791227162; cv=none; b=Iqs/ikb9Ez2q32XCLzxgPQPhEqGlRB6/SHRZt2KTQ0YXEw01/NFDN7xSLFxMGr0X7QwFGY2eB2ITPhxfC8t+q9n4Pw9Vj6SLaYV+Gz78uSd+YPNLGIdQ527KphTQIMzr4cbihAM8E1keqk1dmQI+Kzqdwrro0KH2cRx7j3YtLC8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791227162; c=relaxed/simple; bh=jd3cIebWslGe2SluqUeOouUcjNDtvQn8n5sEySelsZ8=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=O8MgJAELuMxJDmFXIBiMWfqgxuy/TpZMoS23YHmQIkY3KpQA1KbmSXHiQp+J8GvocjTBF9SdkOrq0XRbvApsnXgGb4IqqJzxcyh7BV57gMpuf7H+rtVzYVLnHdE17VH+Nbz5O6BFKyvKd9whJRWHDEwX03OwrcWKpLkzyVirBHo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=nHHkwOPu; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="nHHkwOPu" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A0F0E1F000FF; Mon, 5 Oct 2026 19:06:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791227160; bh=SNODs5FbLpBfmraE85X0V3Oi5UUM7z6D6PE8VhoZEoo=; h=Date:From:To:Cc:Subject:In-Reply-To; b=nHHkwOPuimd70cQZVRVzcCQ1MH+35tAUZ/tpFxE2p8QJbR9YZG5YKTOa5xAN5GzjV 4tW9WcKuG/a90atgTnVKXYmXqT6iZcc9gcEAUYBJHF4gsGCXqsqPvXsO9rLgIz7joC 8xVGt0EtEVvsk8p1zgFVzhPcUuDm8Zqg+v57EFVGzfmfosV6HXHBqa1qR1f5KoXU9Y QQbhJGBwEWa63xjLl8gUhPPU+KKT9yu6UambZmUAFCJ2wu+Nribtw4AQr5s2ljSy1P daMYHhqYhSFt1dQckdGBR1I6J2fTYEEA+brz22UvLqQyLW6qeiMjB3gLkd3kyxw8T9 xg77jhZ2FI9ZQ== Date: Mon, 5 Oct 2026 14:05:59 -0500 From: Bjorn Helgaas To: Yehyeong Lee Cc: jgross@suse.com, sstabellini@kernel.org, oleksandr_tyshchenko@epam.com, bhelgaas@google.com, jbeulich@suse.com, konrad.wilk@oracle.com, xen-devel@lists.xenproject.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Jan Beulich Subject: Re: [PATCH] xen/pcifront: check that an AER callback exists before calling it Message-ID: <20261005190559.GA601702@bhelgaas> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261005133019.284053-1-yhlee@isslab.korea.ac.kr> On Mon, Oct 05, 2026 at 10:30:18PM +0900, Yehyeong Lee wrote: > pcifront_common_process() handles an AER request from the backend by > dispatching on aer_op.cmd to the bound driver's PCI error handler. It > only checks that err_handler and err_handler->error_detected are present, > then for the mmio_enabled, slot_reset and resume commands it calls the > corresponding callback unconditionally. Those three callbacks are > optional -- the PCI core NULL-checks each of them individually before > use -- and many drivers (for example igb, igc, ice and ixgbevf) install > error_detected without all of them. > > aer_op.cmd comes from the shared ring, so a malicious or buggy backend > can send XEN_PCI_OP_aer_mmio (or _slotreset/_resume) for a device whose > driver leaves that callback NULL and make the frontend call through a > NULL pointer, crashing the guest. > > Check each callback before calling it, as the PCI core already does, and > fall through to PCI_ERS_RESULT_NONE when it is absent. > > Fixes: 956a9202cd12 ("xen-pcifront: Xen PCI frontend driver.") > Cc: stable@vger.kernel.org > Signed-off-by: Yehyeong Lee Seems right to me, but I assume the Xen folks will pick this up. Acked-by: Bjorn Helgaas > --- > There is an in-flight fix for a refcount leak in this same function > ("xen/pcifront: Fix PCI device reference leak in AER handling"); this > change is orthogonal and applies in either order. > > drivers/pci/xen-pcifront.c | 13 +++++++++---- > 1 file changed, 9 insertions(+), 4 deletions(-) > > diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c > index cffc32d660327..490913676f244 100644 > --- a/drivers/pci/xen-pcifront.c > +++ b/drivers/pci/xen-pcifront.c > @@ -599,12 +599,17 @@ static pci_ers_result_t pcifront_common_process(int cmd, > case XEN_PCI_OP_aer_detected: > return pdrv->err_handler->error_detected(pcidev, state); > case XEN_PCI_OP_aer_mmio: > - return pdrv->err_handler->mmio_enabled(pcidev); > + if (pdrv->err_handler->mmio_enabled) > + return pdrv->err_handler->mmio_enabled(pcidev); > + break; > case XEN_PCI_OP_aer_slotreset: > - return pdrv->err_handler->slot_reset(pcidev); > + if (pdrv->err_handler->slot_reset) > + return pdrv->err_handler->slot_reset(pcidev); > + break; > case XEN_PCI_OP_aer_resume: > - pdrv->err_handler->resume(pcidev); > - return PCI_ERS_RESULT_NONE; > + if (pdrv->err_handler->resume) > + pdrv->err_handler->resume(pcidev); > + break; > default: > dev_err(&pdev->xdev->dev, > "bad request in aer recovery operation!\n"); > -- > 2.43.0 >