From patchwork Tue Aug 9 13:47:52 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lee Jones X-Patchwork-Id: 12939647 X-Patchwork-Delegate: bpf@iogearbox.net 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 8E483C25B0E for ; Tue, 9 Aug 2022 13:49:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244345AbiHINtl (ORCPT ); Tue, 9 Aug 2022 09:49:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54910 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244316AbiHINsA (ORCPT ); Tue, 9 Aug 2022 09:48:00 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4478217053; Tue, 9 Aug 2022 06:48:00 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id DEF3761166; Tue, 9 Aug 2022 13:47:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3844CC433D6; Tue, 9 Aug 2022 13:47:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1660052879; bh=IQQJyPFnttVbNTaUGHXqrE8BpmegNCUFJ0+ReTCTZu8=; h=From:To:Cc:Subject:Date:From; b=l8Cq0hSkuZnyXUQSYfpxa755uy8qEYAkefS/L+mNsEuVZ8voZcMQp1ONL8XI5lXdV TScVJjrMzmGhL9yhSOc9kqn5FuaCmDqJqQWflx1XS8JwJ/Yf1wCoW1UMKv6TXz7i6T YRJjQRFPVHqQB9ZQnu0P06Kb/sPCIxtAaIJdXDR578J84gh3B5IXoK+sdzBEkgwA1l LkYqe9PH+C7Xqj3fNd5who6h4OMiLfoV9l1SECY9iqVL7mfDW2mWP4Ip7OJW2tLw5f gfrE4DjI7moAUCzMydSt7C5+3SalNH2usvfsCNWVmXw4zVKwFmuK/1gNxONvohhZHn F4AEZea/DhO1Q== From: Lee Jones To: lee@kernel.org Cc: linux-kernel@vger.kernel.org, Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , KP Singh , Stanislav Fomichev , Hao Luo , bpf@vger.kernel.org, Jiri Olsa Subject: [PATCH v3 1/1] bpf: Drop unprotected find_vpid() in favour of find_get_pid() Date: Tue, 9 Aug 2022 14:47:52 +0100 Message-Id: <20220809134752.1488608-1-lee@kernel.org> X-Mailer: git-send-email 2.37.1.559.g78731f0fdb-goog MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net The documentation for find_vpid() clearly states: "Must be called with the tasklist_lock or rcu_read_lock() held." Presently we do neither. Let's use find_get_pid() which searches for the vpid, then takes a reference to it preventing early free, all within the safety of rcu_read_lock(). Once we have our reference we can safely make use of it up until the point it is put. Cc: Alexei Starovoitov Cc: Daniel Borkmann Cc: John Fastabend Cc: Andrii Nakryiko Cc: Martin KaFai Lau Cc: Song Liu Cc: Yonghong Song Cc: KP Singh Cc: Stanislav Fomichev Cc: Hao Luo Cc: bpf@vger.kernel.org Fixes: 41bdc4b40ed6f ("bpf: introduce bpf subcommand BPF_TASK_FD_QUERY") Acked-by: Jiri Olsa Signed-off-by: Lee Jones --- v1 => v2: * Commit log update - description - no code differences v2 => v3: * Commit log update - spelling of find_vpid() - no code differences kernel/bpf/syscall.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 83c7136c5788d..c20cff30581c4 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -4385,6 +4385,7 @@ static int bpf_task_fd_query(const union bpf_attr *attr, const struct perf_event *event; struct task_struct *task; struct file *file; + struct pid *ppid; int err; if (CHECK_ATTR(BPF_TASK_FD_QUERY)) @@ -4396,7 +4397,9 @@ static int bpf_task_fd_query(const union bpf_attr *attr, if (attr->task_fd_query.flags != 0) return -EINVAL; - task = get_pid_task(find_vpid(pid), PIDTYPE_PID); + ppid = find_get_pid(pid); + task = get_pid_task(ppid, PIDTYPE_PID); + put_pid(ppid); if (!task) return -ENOENT;