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Thomas Orgis" , Yiyang Chen Subject: [PATCH 1/2] taskstats: return -EBADF when cgroupstats receives an invalid fd Date: Sat, 11 Jul 2026 04:07:36 +0800 Message-ID: X-Mailer: git-send-email 2.43.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" cgroupstats_user_cmd() returns 0 without sending a reply or a netlink error when the fd passed via CGROUPSTATS_CMD_ATTR_FD does not resolve to an open file in the caller's table. As a result: - clients that did not set NLM_F_ACK block on recv() indefinitely waiting for a CGROUPSTATS_CMD_NEW message that is never emitted; - clients that set NLM_F_ACK receive a misleading "success" ACK (errno =3D=3D 0) with no statistics payload. Return -EBADF instead so the netlink layer propagates the error to userspace as expected. Signed-off-by: Yiyang Chen Reviewed-by: Bradley Morgan --- kernel/taskstats.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/taskstats.c b/kernel/taskstats.c index 2cd0172d0516..8d115670a3ca 100644 --- a/kernel/taskstats.c +++ b/kernel/taskstats.c @@ -423,7 +423,7 @@ static int cgroupstats_user_cmd(struct sk_buff *skb, st= ruct genl_info *info) fd =3D nla_get_u32(info->attrs[CGROUPSTATS_CMD_ATTR_FD]); CLASS(fd, f)(fd); if (fd_empty(f)) - return 0; + return -EBADF; =20 size =3D nla_total_size(sizeof(struct cgroupstats)); =20 --=20 2.43.0 From nobody Sun Jul 26 00:19:22 2026 Received: from mail-pl1-f174.google.com (mail-pl1-f174.google.com [209.85.214.174]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 500E3379C21 for ; Fri, 10 Jul 2026 20:08:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.174 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783714119; cv=none; b=Rs2eqBnxLIBKYpVpix/8kysBeXq6xG1lzfJCBxgGTxyIO+pE4Qb2HdwkCxB19hzZNZjczUDUojYAbNchIdxd1/rfvScTdRyMTkPGN1JLJMyT0kle0PwPNluHghVuY5JmlDKFH3Etr8XYFiofr72XPA7q9C4D8fHlWtCqi/fchFM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783714119; c=relaxed/simple; bh=GH9ahwvzLupXewC5Khh/o2XDiz2luwYMquqdBaLBZE0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=c7Y4SCS13Ydi18AfM8KsBuRJNksEF3scrGD0zBUKJQxO3pYFHPGyVoF0zfbz6+NX6dR9tE7U0IOxZJqXRneqVp3t4TF0K/Zt7KxDy0PchjivVY8XnJvrMHlQA+tQo6sDGjELOJjeb9/ymi7/uEh3FfTuXX81AI1EQixsSR3lcsw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=Y6Sr7QUW; arc=none smtp.client-ip=209.85.214.174 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Y6Sr7QUW" Received: by mail-pl1-f174.google.com with SMTP id d9443c01a7336-2caea3f742bso14344515ad.0 for ; Fri, 10 Jul 2026 13:08:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1783714118; x=1784318918; darn=vger.kernel.org; h=content-transfer-encoding:content-type:mime-version:references :in-reply-to:message-id:date:subject:cc:to:from:from:to:cc:subject :date:message-id:reply-to:content-type; bh=zuCo3MeyfE4QF1kRRNTAZykWAe3DpXfKrt3H+gIHDiw=; b=Y6Sr7QUWzn2RHZp8R030uiYDJ5ap41edzRYFUhG+AkYDZPzUj081EB+vCZiyqIlAe/ WLagaDZ7TMgTgktvdMAHC5cv6SJFqSDak34lpDwfeXoXARhfoGgMQru7ztXDIlbOP5gE vmqqdnNINsnZuxYsZQA1peNpW4f+lJSAKHhr8qpJeoK6gJjDFt3hYlwQQ2WaDUK4Auk6 mvfFT18LcyaEMKrU8VSSCXtEU2eyxF4P7XixcReE5PLBKp/dkbAyEnaCXX1+hpH6Pt0O FNYBr2RjNXqxzegY1J9PZvAutqr1nlPLCTkayZcAksLgmFZxecOplO+yWMU+KBSE6hxC tU1A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1783714118; x=1784318918; h=content-transfer-encoding:content-type:mime-version:references :in-reply-to:message-id:date:subject:cc:to:from:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=zuCo3MeyfE4QF1kRRNTAZykWAe3DpXfKrt3H+gIHDiw=; b=ALPcoY/txPq3LnKbsJ0FM8jyN9QQwDbrCKD9SQa0Iaepmc2kZc3mbJ/NB6uz+PH75R x1dJzS2EBCWxosZfGpJV5zJfCtxy4CHI+MYg8PkDmzVM+Ex9cG19kVrsdGsMh/IVeRpH M2KFbmxq+2556hwExtWfD86Lfb+N/t9v6VEOj+wvxxI+PdDPZCav1GNdxmRDc6Rf+6YF lSlGEMW/Cn7E67JS85FW5K/2cF75h5VDXrF7Kr3YfQiJFj4BUr/wBU2M+0vijzGh8j4V xsxfJrJkyu5LMRurRBi3I66E5UiZIRNBzKpGYr5h7Vpk+VekAkBSNKxIS/k++zoWC+CT wggA== X-Gm-Message-State: AOJu0YzaxcyzA3nkXNJu8tohYtSRJk/DfuP2pV+w+8l1kNrKBjKE8ECg B8wG/wEaAEydVz6feovSbrGfRB5fWk78y+vC7GGbYHn6xCDZrx8NvMDu X-Gm-Gg: AfdE7ck4d1zAPJ+6ode9gQTSO4zGQltBqizBGNiULrJ5uiiLPVroDE7S+tVGa8U7/Vk N3e11MmrVnAA5yh3hI01vVDmxjkq7i0akdEiiKQu1e+V6QQsCu4ChBx8t9azjTyWhIEy7EhorsO +g+tTYdYe4dtluQU8iQFuvBN2k636B7Oz4oTeR8+0TclaffFYoIdL1nOUCASEZTPHcE3F0BNBgf slvHl8biW5m5V9O1+l37mDLuI8uWkqzjxrQtPJL2w8lbhV4RH7M+qTrirSJRulUzRePQSpk/coQ GYDLK5Rs/wrP7BlGMyBZXwOl6T9CaWoI/y5+Tp/phTz/DtayNy8cZfU8DFiCg9mc9mnmr5Yuyjc KjUEDXhqs0flUWnj0OKIrwmgMstiRavELmATU7CLoWDDRzSOiIUXWdINTtpT1/ls5qDopIlwyxU DOojr/o78t1/iA X-Received: by 2002:a17:903:1c8:b0:2ca:ed41:d33d with SMTP id d9443c01a7336-2ce9f294803mr5137365ad.45.1783714117608; Fri, 10 Jul 2026 13:08:37 -0700 (PDT) Received: from ubuntu24.lan ([14.146.16.130]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2ccc9bdb7ddsm65296255ad.1.2026.07.10.13.08.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 10 Jul 2026 13:08:37 -0700 (PDT) From: Yiyang Chen To: Balbir Singh , Andrew Morton Cc: linux-kernel@vger.kernel.org, "Dr . Thomas Orgis" , Yiyang Chen Subject: [PATCH 2/2] selftests/acct: add cgroupstats functional test Date: Sat, 11 Jul 2026 04:07:37 +0800 Message-ID: <2a56921276f0962f97f00863e8c7d3c3f6893d5a.1783713230.git.cyyzero16@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: 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="utf-8" Content-Transfer-Encoding: quoted-printable Add a self-contained test for the CGROUPSTATS_CMD_GET genl command that covers three cases: - querying a cgroup v1 hierarchy and verifying the response contains non-zero task counts - rejecting an invalid fd without NLM_F_ACK - rejecting an invalid fd with NLM_F_ACK Signed-off-by: Yiyang Chen Reviewed-by: Bradley Morgan --- tools/testing/selftests/acct/Makefile | 1 + tools/testing/selftests/acct/cgroupstats.c | 354 +++++++++++++++++++++ 2 files changed, 355 insertions(+) create mode 100644 tools/testing/selftests/acct/cgroupstats.c diff --git a/tools/testing/selftests/acct/Makefile b/tools/testing/selftest= s/acct/Makefile index 083cab5ddb72..db88d65f5581 100644 --- a/tools/testing/selftests/acct/Makefile +++ b/tools/testing/selftests/acct/Makefile @@ -1,6 +1,7 @@ # SPDX-License-Identifier: GPL-2.0 TEST_GEN_PROGS :=3D acct_syscall TEST_GEN_PROGS +=3D taskstats_fill_stats_tgid +TEST_GEN_PROGS +=3D cgroupstats =20 CFLAGS +=3D -Wall LDLIBS +=3D -lpthread diff --git a/tools/testing/selftests/acct/cgroupstats.c b/tools/testing/sel= ftests/acct/cgroupstats.c new file mode 100644 index 000000000000..e2836383ed50 --- /dev/null +++ b/tools/testing/selftests/acct/cgroupstats.c @@ -0,0 +1,354 @@ +// SPDX-License-Identifier: GPL-2.0 +#define _GNU_SOURCE + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include "kselftest.h" + +#ifndef NLA_ALIGN +#define NLA_ALIGNTO 4 +#define NLA_ALIGN(len) (((len) + NLA_ALIGNTO - 1) & ~(NLA_ALIGNTO - 1)) +#define NLA_HDRLEN ((int)NLA_ALIGN(sizeof(struct nlattr))) +#endif + +#define RECV_TIMEOUT_SEC 2 + +static void *nla_data(const struct nlattr *na) +{ + return (void *)((char *)na + NLA_HDRLEN); +} + +static int netlink_open(void) +{ + struct timeval tv =3D { .tv_sec =3D RECV_TIMEOUT_SEC }; + struct sockaddr_nl addr =3D { + .nl_family =3D AF_NETLINK, + .nl_pid =3D getpid(), + }; + int fd; + + fd =3D socket(AF_NETLINK, SOCK_RAW, NETLINK_GENERIC); + if (fd < 0) + return -errno; + + /* + * Ensure that a missing kernel reply fails the individual test + * case instead of hanging the whole test binary. + */ + if (setsockopt(fd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv)) < 0) { + int err =3D -errno; + + close(fd); + return err; + } + + if (bind(fd, (struct sockaddr *)&addr, sizeof(addr)) < 0) { + int err =3D -errno; + + close(fd); + return err; + } + + return fd; +} + +static int send_request(int fd, void *buf, size_t len) +{ + struct sockaddr_nl addr =3D { + .nl_family =3D AF_NETLINK, + }; + + if (sendto(fd, buf, len, 0, (struct sockaddr *)&addr, sizeof(addr)) < 0) + return -errno; + + return 0; +} + +static int get_family_id(int fd, const char *name) +{ + struct { + struct nlmsghdr nlh; + struct genlmsghdr genl; + char buf[256]; + } req =3D { 0 }; + char resp[8192]; + struct nlmsghdr *nlh; + struct genlmsghdr *genl; + struct nlattr *na; + int len; + int rem; + int ret; + + req.nlh.nlmsg_len =3D NLMSG_LENGTH(GENL_HDRLEN); + req.nlh.nlmsg_type =3D GENL_ID_CTRL; + req.nlh.nlmsg_flags =3D NLM_F_REQUEST; + req.nlh.nlmsg_seq =3D 1; + req.nlh.nlmsg_pid =3D getpid(); + + req.genl.cmd =3D CTRL_CMD_GETFAMILY; + req.genl.version =3D 1; + + na =3D (struct nlattr *)((char *)&req + NLMSG_ALIGN(req.nlh.nlmsg_len)); + na->nla_type =3D CTRL_ATTR_FAMILY_NAME; + na->nla_len =3D NLA_HDRLEN + strlen(name) + 1; + memcpy(nla_data(na), name, strlen(name) + 1); + req.nlh.nlmsg_len =3D NLMSG_ALIGN(req.nlh.nlmsg_len) + NLA_ALIGN(na->nla_= len); + + ret =3D send_request(fd, &req, req.nlh.nlmsg_len); + if (ret) + return ret; + + len =3D recv(fd, resp, sizeof(resp), 0); + if (len < 0) + return -errno; + + for (nlh =3D (struct nlmsghdr *)resp; NLMSG_OK(nlh, len); + nlh =3D NLMSG_NEXT(nlh, len)) { + if (nlh->nlmsg_type =3D=3D NLMSG_ERROR) { + struct nlmsgerr *err =3D NLMSG_DATA(nlh); + + return err->error ? err->error : -ENOENT; + } + + genl =3D (struct genlmsghdr *)NLMSG_DATA(nlh); + rem =3D nlh->nlmsg_len - NLMSG_HDRLEN - GENL_HDRLEN; + na =3D (struct nlattr *)((char *)genl + GENL_HDRLEN); + while (rem >=3D (int)sizeof(*na) && + na->nla_len >=3D (int)sizeof(*na) && + na->nla_len <=3D rem) { + if (na->nla_type =3D=3D CTRL_ATTR_FAMILY_ID) + return *(uint16_t *)nla_data(na); + rem -=3D NLA_ALIGN(na->nla_len); + na =3D (struct nlattr *)((char *)na + NLA_ALIGN(na->nla_len)); + } + } + + return -ENOENT; +} + +static int send_cgroupstats_cmd(int fd, int family_id, uint32_t cgroup_fd, + int flags) +{ + struct { + struct nlmsghdr nlh; + struct genlmsghdr genl; + char buf[256]; + } req =3D { 0 }; + struct nlattr *na; + + req.nlh.nlmsg_len =3D NLMSG_LENGTH(GENL_HDRLEN); + req.nlh.nlmsg_type =3D family_id; + req.nlh.nlmsg_flags =3D NLM_F_REQUEST | flags; + req.nlh.nlmsg_seq =3D 2; + req.nlh.nlmsg_pid =3D getpid(); + + req.genl.cmd =3D CGROUPSTATS_CMD_GET; + req.genl.version =3D 1; + + na =3D (struct nlattr *)((char *)&req + NLMSG_ALIGN(req.nlh.nlmsg_len)); + na->nla_type =3D CGROUPSTATS_CMD_ATTR_FD; + na->nla_len =3D NLA_HDRLEN + sizeof(cgroup_fd); + memcpy(nla_data(na), &cgroup_fd, sizeof(cgroup_fd)); + req.nlh.nlmsg_len =3D NLMSG_ALIGN(req.nlh.nlmsg_len) + NLA_ALIGN(na->nla_= len); + + return send_request(fd, &req, req.nlh.nlmsg_len); +} + +/* + * Receive and decode a cgroupstats response. + * + * Returns: + * 0 =E2=80=94 success, stats filled from CGROUPSTATS_CMD_NE= W reply + * <0 =E2=80=94 NLMSG_ERROR errno (e.g. -EBADF, -EINVAL) + */ +static int recv_cgroupstats_response(int fd, struct cgroupstats *stats) +{ + char resp[8192]; + struct nlmsghdr *nlh; + struct genlmsghdr *genl; + struct nlattr *na; + int len; + int rem; + + memset(stats, 0, sizeof(*stats)); + + len =3D recv(fd, resp, sizeof(resp), 0); + if (len < 0) + return -errno; + + for (nlh =3D (struct nlmsghdr *)resp; NLMSG_OK(nlh, len); + nlh =3D NLMSG_NEXT(nlh, len)) { + if (nlh->nlmsg_type =3D=3D NLMSG_ERROR) { + struct nlmsgerr *err =3D NLMSG_DATA(nlh); + + return err->error; + } + + genl =3D (struct genlmsghdr *)NLMSG_DATA(nlh); + if (genl->cmd !=3D CGROUPSTATS_CMD_NEW) + continue; + + rem =3D nlh->nlmsg_len - NLMSG_HDRLEN - GENL_HDRLEN; + na =3D (struct nlattr *)((char *)genl + GENL_HDRLEN); + while (rem >=3D (int)sizeof(*na) && + na->nla_len >=3D (int)sizeof(*na) && + na->nla_len <=3D rem) { + if (na->nla_type =3D=3D CGROUPSTATS_TYPE_CGROUP_STATS) { + memcpy(stats, nla_data(na), sizeof(*stats)); + return 0; + } + rem -=3D NLA_ALIGN(na->nla_len); + na =3D (struct nlattr *)((char *)na + NLA_ALIGN(na->nla_len)); + } + } + + return -EIO; +} + +/* mkdtemp() modifies the template in place, so this cannot be const. */ +static char cg_mountpoint[32]; +static bool cg_mounted; + +static int setup_cgroup_v1(void) +{ + strcpy(cg_mountpoint, "/tmp/cgstats_test_XXXXXX"); + + if (!mkdtemp(cg_mountpoint)) + return -errno; + + if (mount("cgstats_test", cg_mountpoint, "cgroup", 0, + "none,name=3Dcgstats_test") < 0) { + int ret =3D -errno; + + rmdir(cg_mountpoint); + return ret; + } + + cg_mounted =3D true; + return 0; +} + +static void cleanup_cgroup_v1(void) +{ + if (!cg_mounted) + return; + umount2(cg_mountpoint, MNT_DETACH); + rmdir(cg_mountpoint); + cg_mounted =3D false; +} + +int main(void) +{ + struct cgroupstats stats; + uint64_t total_tasks; + int family_id; + int nl_fd; + int cg_fd; + int ret; + + ksft_print_header(); + + nl_fd =3D netlink_open(); + if (nl_fd < 0) + ksft_exit_skip("failed to open generic netlink socket: %s\n", + strerror(-nl_fd)); + + family_id =3D get_family_id(nl_fd, TASKSTATS_GENL_NAME); + if (family_id < 0) + ksft_exit_skip("taskstats generic netlink family unavailable: %s\n", + strerror(-family_id)); + + ksft_set_plan(3); + + /* + * Test 1: mount a private cgroup v1 hierarchy, query it, and + * verify the response contains sane task counts. If the test + * environment cannot create a private cgroup v1 mount, skip this + * case and continue with the unprivileged regression checks below. + */ + ret =3D setup_cgroup_v1(); + if (ret) { + ksft_test_result_skip("cgroupstats query: cannot mount cgroup v1: %s\n", + strerror(-ret)); + } else { + cg_fd =3D open(cg_mountpoint, O_RDONLY | O_DIRECTORY); + if (cg_fd < 0) { + ksft_test_result_fail("cgroupstats query: open mountpoint: %s\n", + strerror(errno)); + } else { + ret =3D send_cgroupstats_cmd(nl_fd, family_id, + (uint32_t)cg_fd, 0); + if (ret) { + ksft_test_result_fail("cgroupstats query: send: %s\n", + strerror(-ret)); + } else { + ret =3D recv_cgroupstats_response(nl_fd, &stats); + if (ret < 0) { + ksft_test_result_fail("cgroupstats query: %s\n", + strerror(-ret)); + } else { + total_tasks =3D (uint64_t)stats.nr_sleeping + + (uint64_t)stats.nr_running + + (uint64_t)stats.nr_stopped + + (uint64_t)stats.nr_uninterruptible + + (uint64_t)stats.nr_io_wait; + + ksft_print_msg("cgroupstats query: total_tasks=3D%llu\n", + (unsigned long long)total_tasks); + + ksft_test_result(total_tasks > 0, + "cgroupstats query returns valid stats\n"); + } + } + close(cg_fd); + } + } + cleanup_cgroup_v1(); + + /* + * Test 2: invalid fd without NLM_F_ACK. The kernel should + * return -EBADF via NLMSG_ERROR regardless of whether the + * client requested an explicit ACK. + */ + ret =3D send_cgroupstats_cmd(nl_fd, family_id, 0xFFFFFFFF, 0); + if (ret) + ksft_exit_fail_msg("send test 2 failed: %s\n", strerror(-ret)); + + ret =3D recv_cgroupstats_response(nl_fd, &stats); + ksft_print_msg("bad fd (no ACK): response=3D%d (%s)\n", + ret, ret < 0 ? strerror(-ret) : "unexpected success"); + ksft_test_result(ret =3D=3D -EBADF, + "cgroupstats rejects bad fd without NLM_F_ACK\n"); + + /* + * Test 3: invalid fd with NLM_F_ACK. Same expectation as + * test 2, but exercised through a different netlink flag + * path in the kernel's ack/error handling. + */ + ret =3D send_cgroupstats_cmd(nl_fd, family_id, 0xFFFFFFFF, NLM_F_ACK); + if (ret) + ksft_exit_fail_msg("send test 3 failed: %s\n", strerror(-ret)); + + ret =3D recv_cgroupstats_response(nl_fd, &stats); + ksft_print_msg("bad fd (with ACK): response=3D%d (%s)\n", + ret, ret < 0 ? strerror(-ret) : "unexpected success"); + ksft_test_result(ret =3D=3D -EBADF, + "cgroupstats rejects bad fd with NLM_F_ACK\n"); + + close(nl_fd); + ksft_finished(); + return ksft_get_fail_cnt() ? KSFT_FAIL : KSFT_PASS; +} --=20 2.43.0