From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DC547C25B47 for ; Mon, 23 Oct 2023 18:03:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231339AbjJWSDS (ORCPT ); Mon, 23 Oct 2023 14:03:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49882 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229807AbjJWSDR (ORCPT ); Mon, 23 Oct 2023 14:03:17 -0400 Received: from mail-pl1-x630.google.com (mail-pl1-x630.google.com [IPv6:2607:f8b0:4864:20::630]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C7CBDB4 for ; Mon, 23 Oct 2023 11:03:14 -0700 (PDT) Received: by mail-pl1-x630.google.com with SMTP id d9443c01a7336-1cac80292aeso19751665ad.1 for ; Mon, 23 Oct 2023 11:03:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1698084194; x=1698688994; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=arV3WvwMGkVwizBfpgtp9qoHNsxotQwpgBb6OnpwjQI=; b=G2vbIiTwgvKjW4QilPTMiM9Uz2YF2WKxk6dY6fqoDkc5Lb1WNjVBeTLPqJc/BryPdW ISjJ7q8/qP2gvFYEpBEWIi+8xJi2SwrZnwdkRRXwybKZ65+TeG8eHwj41VMTv57LXoRD bmyaPKEO9aPOjWMoydK/eWHQMkkLW1d5S0SHfAFv+XjjUwUvtw0c9oKQyg+PxSYX4pCo uT7MnbZ2Rf77SiRfGeJnkuuJEXetHWl9P7G5FbrW3ALSwufAD2ypa8+kze9rm2Z2xIa8 2bvLltF6ehd5kpONCoOrxSJcfaZjaezxqVXjUQxnUMl3d8HDNdbBCSWA/U6lFRhsVlbK bQPA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1698084194; x=1698688994; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=arV3WvwMGkVwizBfpgtp9qoHNsxotQwpgBb6OnpwjQI=; b=cxTozpGY7n9uL2mD7vN/EpNOzPYQxICcKw4nDuCmohgrtUGKMgqUuBN1n2fR4Rl6Fd 3htRNiv/heBFRcfN3NBsfT6Hi3kwQghbHbrlhmGK9dTsfeoTKC2/0w2/XVjwHfFqyvS7 P3ffsGIetemS96AEJdlFTojQtcWNVno6myYtX36OBxJb6kAaRIxP2VbonewlQClhrsrT rUOvIeFg5Gxvl7YtpF6Xu4lyKSS/GffsA+JGlpQvWiv4tFLf9bCC8U5DSmb3W2h2GYXb HM3No12ENpeHEOsHofdK023jiFy0rBGRsjdCGC53pKJr6KyvGSVAT2OIJwZD+WWXe/XZ IzsA== X-Gm-Message-State: AOJu0Yy/jj9R+o5df8MxDa2lP+yilRFL38/E/NmIhuKjnUgLJPgJQdxs vycnrEzMeM0HHelgcP4DxhVLtA== X-Google-Smtp-Source: AGHT+IFqDzcfSPSj6ToWBgpfG/3z9qkyMrDNHGYQJ5K5TCb2lJU2I3IY/Qp9PsSJ/FDNmIuZzk9wxA== X-Received: by 2002:a17:902:dac9:b0:1ca:9415:a50d with SMTP id q9-20020a170902dac900b001ca9415a50dmr9099665plx.2.1698084194201; Mon, 23 Oct 2023 11:03:14 -0700 (PDT) Received: from p14s ([2604:3d09:148c:c800:85b7:8283:12b2:30f8]) by smtp.gmail.com with ESMTPSA id a8-20020a170902ecc800b001b8a2edab6asm6182119plh.244.2023.10.23.11.03.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Oct 2023 11:03:13 -0700 (PDT) Date: Mon, 23 Oct 2023 12:03:11 -0600 From: Mathieu Poirier To: Justin Stitt Cc: Bjorn Andersson , linux-remoteproc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH] rpmsg: virtio: replace deprecated strncpy with strscpy/_pad Message-ID: References: <20231021-strncpy-drivers-rpmsg-virtio_rpmsg_bus-c-v1-1-8abb919cbe24@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231021-strncpy-drivers-rpmsg-virtio_rpmsg_bus-c-v1-1-8abb919cbe24@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Justin, On Sat, Oct 21, 2023 at 12:09:16AM +0000, Justin Stitt wrote: > strncpy() is deprecated for use on NUL-terminated destination strings > [1] and as such we should prefer more robust and less ambiguous string > interfaces. > > This patch replaces 3 callsites of strncpy(). > > The first two populate the destination buffer `nsm.name` -- which we > expect to be NUL-terminated based on their use with format strings. > > Firstly, as I understand it, virtio_rpmsg_announce_create() creates an > rpmsg_ns_msg and sends via: > > virtio_rpmsg_bus.c: > 336: err = rpmsg_sendto(rpdev->ept, &nsm, sizeof(nsm), RPMSG_NS_ADDR); > > ... which uses: > virtio_rpmsg_sendto() -> rpmsg_send_offchannel_raw() > > ... which copies its data into an rpmsg_hdr `msg` in virtio_rpmsg_bus.c > 618: memcpy(msg->data, data, len); > > ... and we end up receiving here via a callback: > Function rpmsg_ns_cb() is called when a message is received from the remote processor and not on the downward path from rpmsg_send_offchannel_raw(). I am good with the code modification but the changelog needs to be amended. > rpmsg_ns.c: > 30: /* invoked when a name service announcement arrives */ > 31: static int rpmsg_ns_cb(struct rpmsg_device *rpdev, void *data, int len, > 32: void *priv, u32 src) > 33: { > 34: struct rpmsg_ns_msg *msg = data; > ... > 50: /* don't trust the remote processor for null terminating the name */ > 51: msg->name[RPMSG_NAME_SIZE - 1] = '\0'; > > ... which finally leads into the use of `name` within a format string: > rpmsg_ns.c: > 57: dev_info(dev, "%sing channel %s addr 0x%x\n", > 58: rpmsg32_to_cpu(rpdev, msg->flags) & RPMSG_NS_DESTROY ? > 59: "destroy" : "creat", msg->name, chinfo.dst); > > Taking another look at this comment + NUL-byte assignment: > 50: /* don't trust the remote processor for null terminating the name */ > 51: msg->name[RPMSG_NAME_SIZE - 1] = '\0'; > > ... we probably _can_ trust that this string is NUL-terminated with the > introduction of strscpy(). However, since there might be some magic > happening between the announcement create and the callback that I don't > understand, I've opted to leave this comment and assignment alone as it > doesn't hurt. > > We can also observe that `nsm` is not zero-initialized and as such we > should maintain the NUL-padding behavior that strncpy() provides: > > virtio_rpmsg_bus.c: > 330: struct rpmsg_ns_msg nsm; > > Considering the above, a suitable replacement is `strscpy_pad` due to > the fact that it guarantees both NUL-termination and NUL-padding on the > destination buffer. > > Now, for the third and final destination buffer rpdev->id.name we can > just go for strscpy() (not _pad()) as rpdev points to &vch->rpdev: > | rpdev = &vch->rpdev; > > ... and vch is zero-allocated: > | vch = kzalloc(sizeof(*vch), GFP_KERNEL); > > ... this renders any additional NUL-byte assignments (like the ones > strncpy() or strscpy_pad() does) redundant. I agree with the above rational. Thanks, Mathieu > > Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1] > Link: https://github.com/KSPP/linux/issues/90 > Cc: linux-hardening@vger.kernel.org > Signed-off-by: Justin Stitt > --- > Note: build-tested only. > > Found with: $ rg "strncpy\(" > --- > drivers/rpmsg/virtio_rpmsg_bus.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c > index 905ac7910c98..dc87965f8164 100644 > --- a/drivers/rpmsg/virtio_rpmsg_bus.c > +++ b/drivers/rpmsg/virtio_rpmsg_bus.c > @@ -329,7 +329,7 @@ static int virtio_rpmsg_announce_create(struct rpmsg_device *rpdev) > virtio_has_feature(vrp->vdev, VIRTIO_RPMSG_F_NS)) { > struct rpmsg_ns_msg nsm; > > - strncpy(nsm.name, rpdev->id.name, RPMSG_NAME_SIZE); > + strscpy_pad(nsm.name, rpdev->id.name, sizeof(nsm.name)); > nsm.addr = cpu_to_rpmsg32(rpdev, rpdev->ept->addr); > nsm.flags = cpu_to_rpmsg32(rpdev, RPMSG_NS_CREATE); > > @@ -353,7 +353,7 @@ static int virtio_rpmsg_announce_destroy(struct rpmsg_device *rpdev) > virtio_has_feature(vrp->vdev, VIRTIO_RPMSG_F_NS)) { > struct rpmsg_ns_msg nsm; > > - strncpy(nsm.name, rpdev->id.name, RPMSG_NAME_SIZE); > + strscpy_pad(nsm.name, rpdev->id.name, sizeof(nsm.name)); > nsm.addr = cpu_to_rpmsg32(rpdev, rpdev->ept->addr); > nsm.flags = cpu_to_rpmsg32(rpdev, RPMSG_NS_DESTROY); > > @@ -424,7 +424,7 @@ static struct rpmsg_device *__rpmsg_create_channel(struct virtproc_info *vrp, > */ > rpdev->announce = rpdev->src != RPMSG_ADDR_ANY; > > - strncpy(rpdev->id.name, chinfo->name, RPMSG_NAME_SIZE); > + strscpy(rpdev->id.name, chinfo->name, sizeof(rpdev->id.name)); > > rpdev->dev.parent = &vrp->vdev->dev; > rpdev->dev.release = virtio_rpmsg_release_device; > > --- > base-commit: 9c5d00cb7b6bbc5a7965d9ab7d223b5402d1f02c > change-id: 20231020-strncpy-drivers-rpmsg-virtio_rpmsg_bus-c-dba15db4e890 > > Best regards, > -- > Justin Stitt >