From patchwork Sat Oct 21 00:09:16 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Justin Stitt X-Patchwork-Id: 13431294 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (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 DEA6A19E for ; Sat, 21 Oct 2023 00:09:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="FEzexuUu" Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 62E0BD66 for ; Fri, 20 Oct 2023 17:09:17 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id 3f1490d57ef6-d9a3a38b96cso1739455276.0 for ; Fri, 20 Oct 2023 17:09:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1697846956; x=1698451756; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=aAAEOjN763/uoJltIk1A5v8Y5KhewbirWplELVB65Hg=; b=FEzexuUu2gcyjH/m+gDOPV0n1SYa1thoit5FP4FvyxKLGhkaVAJTIJYlugs40FEnYh SNPyFghvuKez04npHDSy/eWRyFQVUjHvo6h9Ro6IoRKjlrhW0pUzrnqLglaRvgnkxJzu 2uewqy1+yyx/R0hbwRRXsJ5ZgvT9X+ko26jAlWsapOtvyzmBxp27NmBnduYEBD0X3HQj CHlk+Wdc7dhkAQJPTu90uQARCkKRtvRAs3bdX03zFcaQyzZuNex8rxmcw6xdNIo/bCX/ UOmz5Tv2iOOULyxVzpYce+cvx6w0ZfZGmSvFsbjOAJ8CGFOxLzeqPiTTyeqcs8gLVS/I 9Ekg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1697846956; x=1698451756; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=aAAEOjN763/uoJltIk1A5v8Y5KhewbirWplELVB65Hg=; b=haJTr4PabJfuj51HRMhE15XEQoH5VSegYNr8yR+185S9XA50mu00nqYyWTckHyd/Ck 7OMGdBSEj2wzuAKL5+C5kV8Ffdf2HFRcyTMq2A8laPtnQJJxaHP5MpROs1llfVj66ZWn M0HVSZspHwZtIv3iIf2AF4PL0RHxDVvByPo1Meh3JeGAH5OG8tqnv199kxUHSOC1fQU6 nNAXKCKSysUSxtTlP2vD9TtJ8Bx2Fra7zNs5fSnyEawm5E6mXuIDT1FncZl4r2NVUmMr v8p2MQ3fc6JE6DoHAz9j148tG7mF58G3G2H7BdpW2l9QFbLb7vmR+JguNxw3Ma0bnXFk 0x0w== X-Gm-Message-State: AOJu0Yzr2qe7JLKrR23rIXPMebbdSancxjDktHnx+z/2W20TkDhrwiVA CTdIiAf3Dd7MxoMb9oNbRON8eOlOKnSzr2slxg== X-Google-Smtp-Source: AGHT+IFpzvvP/9vgkVU2kVoCF+uGskkvTbuaun/yXzswon2zQMJ9UpaTPtQnAg54Y5CT+D17i4Ceq6Ey02j9Tbzzvg== X-Received: from jstitt-linux1.c.googlers.com ([fda3:e722:ac3:cc00:2b:ff92:c0a8:23b5]) (user=justinstitt job=sendgmr) by 2002:a25:d252:0:b0:d9a:6658:1781 with SMTP id j79-20020a25d252000000b00d9a66581781mr67180ybg.10.1697846956675; Fri, 20 Oct 2023 17:09:16 -0700 (PDT) Date: Sat, 21 Oct 2023 00:09:16 +0000 Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-B4-Tracking: v=1; b=H4sIAKsWM2UC/x3NQQqDMBBA0avIrDuQxAq2VylFTDLqLBrDjA0V8 e4NLt/m/wOUhEnh2RwgVFh5TRX21kBYxjQTcqwGZ1xrjTOom6SQd4zChURR8kdnLCwbr8OFwX8 VA0Y/2i76O/UPAzWXhSb+XavX+zz/bFkoD3oAAAA= X-Developer-Key: i=justinstitt@google.com; a=ed25519; pk=tC3hNkJQTpNX/gLKxTNQKDmiQl6QjBNCGKJINqAdJsE= X-Developer-Signature: v=1; a=ed25519-sha256; t=1697846955; l=4664; i=justinstitt@google.com; s=20230717; h=from:subject:message-id; bh=KLFJyNnpM1iVE3WDYzVJJsiktCAThrMEX50yU5r+lYk=; b=e8EZde/IM2Lq6ijjTb85ST0CmHeBuSAs4OUmV50+qTd8PO+Az/pSH2VINMLGHg6qz1KlFbldz tk2ycf+PdWJB3PzOu2tAX06XZVnpTD5ejcZdyfi0K4KMoOEPiPt7joV X-Mailer: b4 0.12.3 Message-ID: <20231021-strncpy-drivers-rpmsg-virtio_rpmsg_bus-c-v1-1-8abb919cbe24@google.com> Subject: [PATCH] rpmsg: virtio: replace deprecated strncpy with strscpy/_pad From: Justin Stitt To: Bjorn Andersson , Mathieu Poirier Cc: linux-remoteproc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, Justin Stitt 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: 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. 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(-) --- base-commit: 9c5d00cb7b6bbc5a7965d9ab7d223b5402d1f02c change-id: 20231020-strncpy-drivers-rpmsg-virtio_rpmsg_bus-c-dba15db4e890 Best regards, -- Justin Stitt 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;