From nobody Tue Dec 16 18:33:12 2025 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 1E552C41535 for ; Tue, 12 Dec 2023 21:17:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1377531AbjLLVRk (ORCPT ); Tue, 12 Dec 2023 16:17:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59226 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229541AbjLLVRh (ORCPT ); Tue, 12 Dec 2023 16:17:37 -0500 Received: from mail-pl1-x62b.google.com (mail-pl1-x62b.google.com [IPv6:2607:f8b0:4864:20::62b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C784ABC for ; Tue, 12 Dec 2023 13:17:42 -0800 (PST) Received: by mail-pl1-x62b.google.com with SMTP id d9443c01a7336-1d0b2752dc6so54812055ad.3 for ; Tue, 12 Dec 2023 13:17:42 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1702415862; x=1703020662; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=YgP6QDGYW90+EPtUKh6hhExTw/nr/8L1WXYuh71GNlI=; b=EBII8CWqTewHCYUKQvaukG1zWeJjB2pl/RbMg+j8fFcvUq11md9ygurXaQ0F8RZJRd QN9d/19YNp3UbZ8oh9br9LCWCn2S3HP6xRQ592cXogzBEjuqKMlAo7D2tjJgS0BmhQwY x3edF44sbx8FhzObBflU+lF0Lssb3eOq3JnHc= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1702415862; x=1703020662; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=YgP6QDGYW90+EPtUKh6hhExTw/nr/8L1WXYuh71GNlI=; b=iuhE7Nkn8Reo7m6bFH0pWTKdAC6Ae3+H5cnNOjBqs3/dbY6tFHDJT7hBwnPxRt3FUm fJfk7Fo+zxsA8v2rJLZrLIQVFHDkshB9Ni3P4o62jOLSnMetgm3s/e6vDdJNS8JB8U9V upTdCJkyZDRwKA8B8OvBY1/V/qZ96Byucqz96GHtsH9YvQgkb2sh9soyXpmTUuTfYN05 wM3DCA1TM58cLdtNyrLp7+SzHWu6oa1MdOQSPs+S200sUCLj76QSXz0nKIY3GYNN9fZR 8+KT0z4chNyH9d1+uxbo4UIcTF8fKvtLCdiYSylgzA7jH04hOT6/Typ384iCujEayVhG U43Q== X-Gm-Message-State: AOJu0YyR/cbIYnwwSr5UoDdYPmjaGi7l8kxdDHEixt6sntj1YdvOWikR pyvqFOc9bqQyMQbIqqm17gCAhg== X-Google-Smtp-Source: AGHT+IFjDgIDgEDyV0NYMtC7wrznCUmiU5/lWSweOP8HyZzQAO0+By9K4rXrnLgAr+Ii7qKKdIvgKg== X-Received: by 2002:a17:902:e74e:b0:1cc:5e1b:98b5 with SMTP id p14-20020a170902e74e00b001cc5e1b98b5mr7270093plf.66.1702415862230; Tue, 12 Dec 2023 13:17:42 -0800 (PST) Received: from www.outflux.net (198-0-35-241-static.hfc.comcastbusiness.net. [198.0.35.241]) by smtp.gmail.com with ESMTPSA id g14-20020a1709029f8e00b001cf7c07be50sm9052322plq.58.2023.12.12.13.17.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 Dec 2023 13:17:41 -0800 (PST) From: Kees Cook To: Greg Kroah-Hartman Cc: Kees Cook , Tejun Heo , Zefan Li , Johannes Weiner , Waiman Long , cgroups@vger.kernel.org, Azeem Shaikh , Christophe JAILLET , linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH v3 3/3] kernfs: Convert kernfs_path_from_node_locked() from strlcpy() to strscpy() Date: Tue, 12 Dec 2023 13:17:40 -0800 Message-Id: <20231212211741.164376-3-keescook@chromium.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231212211606.make.155-kees@kernel.org> References: <20231212211606.make.155-kees@kernel.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=8042; i=keescook@chromium.org; h=from:subject; bh=shZXUYfHvcn83JB9rTJeaRzUZqZ1UgzjWRrQTVCVtxU=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBleM30G+t8NV/vyHSFzjkC+K+Zj47yXA4kAs33K S4H3DoxNmuJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZXjN9AAKCRCJcvTf3G3A JkyTEAConGhiBLHsocQ8sbSwq6RTnjeVAFv2A72J5kJK8MHW3sFiydk6ragXK0H4NjhddAT6k9R Iwpc+sAMeXtC5LSHlbkxzwxmAmTpvdZ0+HkpGNofYnO1GRBS2tNZQBx2xovmaBZGLhI3uL1S2Mf uFy1jEp7IRjwOUbM1zHWV4bM+TLIxRHQDtwtec7aUCS9kz92muBO+LZI8wOqu3//0chhPA/oJYK OmIQjfULUR5a/IzcHJAYVXdcRoDKXwclSWSFPM/lbR+ZX7XOdatfwteancUB7mA3VqMASoK6jzD /WWodvOyGvMywKDybb9iVwPwLdcDqi6f6YRwUsKHrO1PU0X/vaRreWv0AW+McpdjcGDDak159n5 dLG/EkNlTRggxw61NNRmjuUIplvXSnvWAMjv1qumw8iiEzajnLTxs+d3rF7yWOneFFWz8cuucBs T6q984RP+2VM4dWIU9dRcdMhF4+sfRiXBnCq95xZcrcakrbEqaZ1G6JMiaKn+pTpTGFBrSw9CAT 91oa2XERahlLlqpV8VMm0QS8tptziqLPqdU3+jQq45xdbDLw4g26B01O8G9PkgXEBkYxNXi2CfE mc85dyxzgFB/wBjBPh0kEN9HaDc4FwRSQ25SkObRCYaStboeynzw51FRZV/pJz/aF6MJJlMUqNu aYQ0Cy79yRW6wZg== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" One of the last remaining users of strlcpy() in the kernel is kernfs_path_from_node_locked(), which passes back the problematic "length we _would_ have copied" return value to indicate truncation. Convert the chain of all callers to use the negative return value (some of which already doing this explicitly). All callers were already also checking for negative return values, so the risk to missed checks looks very low. In this analysis, it was found that cgroup1_release_agent() actually didn't handle the "too large" condition, so this is technically also a bug fix. :) Here's the chain of callers, and resolution identifying each one as now handling the correct return value: kernfs_path_from_node_locked() kernfs_path_from_node() pr_cont_kernfs_path() returns void kernfs_path() sysfs_warn_dup() return value ignored cgroup_path() blkg_path() bfq_bic_update_cgroup() return value ignored TRACE_IOCG_PATH() return value ignored TRACE_CGROUP_PATH() return value ignored perf_event_cgroup() return value ignored task_group_path() return value ignored damon_sysfs_memcg_path_eq() return value ignored get_mm_memcg_path() return value ignored lru_gen_seq_show() return value ignored cgroup_path_from_kernfs_id() return value ignored cgroup_show_path() already converted "too large" error to negative val= ue cgroup_path_ns_locked() cgroup_path_ns() bpf_iter_cgroup_show_fdinfo() return value ignored cgroup1_release_agent() wasn't checking "too large" error proc_cgroup_show() already converted "too large" to negative v= alue Cc: Greg Kroah-Hartman Cc: Tejun Heo Cc: Zefan Li Cc: Johannes Weiner Cc: Waiman Long Cc: cgroups@vger.kernel.org Co-developed-by: Azeem Shaikh Signed-off-by: Azeem Shaikh Link: https://lore.kernel.org/r/20231116192127.1558276-3-keescook@chromium.= org Signed-off-by: Kees Cook --- fs/kernfs/dir.c | 34 +++++++++++++++++----------------- kernel/cgroup/cgroup-v1.c | 2 +- kernel/cgroup/cgroup.c | 4 ++-- kernel/cgroup/cpuset.c | 2 +- 4 files changed, 21 insertions(+), 21 deletions(-) diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c index 8c0e5442597e..8ec73f6cf6ec 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -127,7 +127,7 @@ static struct kernfs_node *kernfs_common_ancestor(struc= t kernfs_node *a, * * [3] when @kn_to is %NULL result will be "(null)" * - * Return: the length of the full path. If the full length is equal to or + * Return: the length of the constructed path. If the path would have been * greater than @buflen, @buf contains the truncated path with the trailing * '\0'. On error, -errno is returned. */ @@ -138,16 +138,17 @@ static int kernfs_path_from_node_locked(struct kernfs= _node *kn_to, struct kernfs_node *kn, *common; const char parent_str[] =3D "/.."; size_t depth_from, depth_to, len =3D 0; + ssize_t copied; int i, j; =20 if (!kn_to) - return strlcpy(buf, "(null)", buflen); + return strscpy(buf, "(null)", buflen); =20 if (!kn_from) kn_from =3D kernfs_root(kn_to)->kn; =20 if (kn_from =3D=3D kn_to) - return strlcpy(buf, "/", buflen); + return strscpy(buf, "/", buflen); =20 common =3D kernfs_common_ancestor(kn_from, kn_to); if (WARN_ON(!common)) @@ -158,18 +159,19 @@ static int kernfs_path_from_node_locked(struct kernfs= _node *kn_to, =20 buf[0] =3D '\0'; =20 - for (i =3D 0; i < depth_from; i++) - len +=3D strlcpy(buf + len, parent_str, - len < buflen ? buflen - len : 0); + for (i =3D 0; i < depth_from; i++) { + copied =3D strscpy(buf + len, parent_str, buflen - len); + if (copied < 0) + return copied; + len +=3D copied; + } =20 /* Calculate how many bytes we need for the rest */ for (i =3D depth_to - 1; i >=3D 0; i--) { for (kn =3D kn_to, j =3D 0; j < i; j++) kn =3D kn->parent; - len +=3D strlcpy(buf + len, "/", - len < buflen ? buflen - len : 0); - len +=3D strlcpy(buf + len, kn->name, - len < buflen ? buflen - len : 0); + + len +=3D scnprintf(buf + len, buflen - len, "/%s", kn->name); } =20 return len; @@ -214,7 +216,7 @@ int kernfs_name(struct kernfs_node *kn, char *buf, size= _t buflen) * path (which includes '..'s) as needed to reach from @from to @to is * returned. * - * Return: the length of the full path. If the full length is equal to or + * Return: the length of the constructed path. If the path would have been * greater than @buflen, @buf contains the truncated path with the trailing * '\0'. On error, -errno is returned. */ @@ -265,12 +267,10 @@ void pr_cont_kernfs_path(struct kernfs_node *kn) sz =3D kernfs_path_from_node(kn, NULL, kernfs_pr_cont_buf, sizeof(kernfs_pr_cont_buf)); if (sz < 0) { - pr_cont("(error)"); - goto out; - } - - if (sz >=3D sizeof(kernfs_pr_cont_buf)) { - pr_cont("(name too long)"); + if (sz =3D=3D -E2BIG) + pr_cont("(name too long)"); + else + pr_cont("(error)"); goto out; } =20 diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c index 76db6c67e39a..9cb00ebe9ac6 100644 --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c @@ -802,7 +802,7 @@ void cgroup1_release_agent(struct work_struct *work) goto out_free; =20 ret =3D cgroup_path_ns(cgrp, pathbuf, PATH_MAX, &init_cgroup_ns); - if (ret < 0 || ret >=3D PATH_MAX) + if (ret < 0) goto out_free; =20 argv[0] =3D agentbuf; diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 4b9ff41ca603..8d2674c6aaef 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -1893,7 +1893,7 @@ int cgroup_show_path(struct seq_file *sf, struct kern= fs_node *kf_node, len =3D kernfs_path_from_node(kf_node, ns_cgroup->kn, buf, PATH_MAX); spin_unlock_irq(&css_set_lock); =20 - if (len >=3D PATH_MAX) + if (len =3D=3D -E2BIG) len =3D -ERANGE; else if (len > 0) { seq_escape(sf, buf, " \t\n\\"); @@ -6301,7 +6301,7 @@ int proc_cgroup_show(struct seq_file *m, struct pid_n= amespace *ns, if (cgroup_on_dfl(cgrp) || !(tsk->flags & PF_EXITING)) { retval =3D cgroup_path_ns_locked(cgrp, buf, PATH_MAX, current->nsproxy->cgroup_ns); - if (retval >=3D PATH_MAX) + if (retval =3D=3D -E2BIG) retval =3D -ENAMETOOLONG; if (retval < 0) goto out_unlock; diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 615daaf87f1f..fb29158ae825 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -4941,7 +4941,7 @@ int proc_cpuset_show(struct seq_file *m, struct pid_n= amespace *ns, retval =3D cgroup_path_ns(css->cgroup, buf, PATH_MAX, current->nsproxy->cgroup_ns); css_put(css); - if (retval >=3D PATH_MAX) + if (retval =3D=3D -E2BIG) retval =3D -ENAMETOOLONG; if (retval < 0) goto out_free; --=20 2.34.1