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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 70980CCD1BF for ; Tue, 28 Oct 2025 16:31:51 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D2C9A8017C; Tue, 28 Oct 2025 12:31:50 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D04288013F; Tue, 28 Oct 2025 12:31:50 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C19F78017C; Tue, 28 Oct 2025 12:31:50 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id B02E58013F for ; Tue, 28 Oct 2025 12:31:50 -0400 (EDT) Received: from smtpin04.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 6A94412ABAE for ; Tue, 28 Oct 2025 16:31:50 +0000 (UTC) X-FDA: 84048064380.04.C8E0EF3 Received: from out-188.mta0.migadu.com (out-188.mta0.migadu.com [91.218.175.188]) by imf16.hostedemail.com (Postfix) with ESMTP id 97244180014 for ; Tue, 28 Oct 2025 16:31:48 +0000 (UTC) Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=UsFMAVyw; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf16.hostedemail.com: domain of roman.gushchin@linux.dev designates 91.218.175.188 as permitted sender) smtp.mailfrom=roman.gushchin@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1761669108; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=HWSSRHmArf/3utDL/ehBcqRMhr+v6BRpRpOeVW9o8r8=; b=salBMRhhFsSrNmqDvjAX1tWMfZPNyilMLueiXCM66J8dWZUXXQ0x46VPPj78QvTxnahBEF JIszjzKpgkaUb4dWlOstom1xz7d8nkjpXkAoxGFNiShiNg+QVsvXWfZ2koMCU6qfo6lyBt pYuNK1czWUwkiVBMg8uTpn3w9J7F890= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1761669108; a=rsa-sha256; cv=none; b=NvtfEoBBpfkf5CKYom6V1LxYLbmQi4jHYZ73NuBUnKUDhdun8BY3pTJmsV6ETNONqDxBW/ U0dpc1KnPHXeqRYIVqsS2r/3Dy2mDWeN5rpoOtCF/RgSJTDQsnhAjOiopPKJVRWrkw7rbf WceLDg5xdnpN9491+8uBbCb+AFKhODg= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=UsFMAVyw; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf16.hostedemail.com: domain of roman.gushchin@linux.dev designates 91.218.175.188 as permitted sender) smtp.mailfrom=roman.gushchin@linux.dev X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1761669105; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=HWSSRHmArf/3utDL/ehBcqRMhr+v6BRpRpOeVW9o8r8=; b=UsFMAVywaT8IpkoioAmt6vXomW1hLiGke5lnfdOFm6CT75B6FrTgPwndxR0Ld4UWB+GB6Z kNutJOjE/CXohXqu1fHCO5Wo3THXTOtts+MdPLoZN5i9dq8L67okdhsPKyc4EOyrIZ69wY ts6Gbva7I2Aaj5nD5s2hWpcBahe3SXQ= From: Roman Gushchin To: bot+bpf-ci@kernel.org Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, ast@kernel.org, surenb@google.com, mhocko@kernel.org, shakeel.butt@linux.dev, hannes@cmpxchg.org, andrii@kernel.org, inwardvessel@gmail.com, linux-mm@kvack.org, cgroups@vger.kernel.org, bpf@vger.kernel.org, martin.lau@kernel.org, song@kernel.org, memxor@gmail.com, tj@kernel.org, daniel@iogearbox.net, eddyz87@gmail.com, yonghong.song@linux.dev, clm@meta.com, ihor.solodrai@linux.dev Subject: Re: [PATCH v2 17/23] bpf: selftests: introduce read_cgroup_file() helper In-Reply-To: <58dd6b759499f212f626e6d7658dd558b3e6a334e0780898002cb2cb84dbcb85@mail.kernel.org> (bot's message of "Mon, 27 Oct 2025 23:48:24 +0000 (UTC)") References: <20251027232206.473085-7-roman.gushchin@linux.dev> <58dd6b759499f212f626e6d7658dd558b3e6a334e0780898002cb2cb84dbcb85@mail.kernel.org> Date: Tue, 28 Oct 2025 09:31:38 -0700 Message-ID: <87ms5b3s45.fsf@linux.dev> MIME-Version: 1.0 Content-Type: text/plain X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Queue-Id: 97244180014 X-Rspamd-Server: rspam02 X-Stat-Signature: df94j5stcfswzamrjczgix9c6fbi8j5x X-HE-Tag: 1761669108-95227 X-HE-Meta: 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 RWCuhSep 8nip9NAGCE7gUDjkrWKaDpMymZVIstEMDe14ClVz2TMUguflPdPPJSC7g+7JDvOGxyO0OucD8vdF1Q7stmS8pLzCllAfDy0Y0yhym5W9+35oKPKauG27LglmuIIGWAO+JLDLiC45ldB48GuzLug1L8drvewYT2vLVNa1iskT0NPuuig/hvnYvsipEDNkcm1Vow/CReaYLPBEkKNJeaXnIzkd5VTk+EdOFIR82CNRyYi29RN92O0ZWgG/zCj7y+D65QWhwzNZ/dDvwFfkprqsShYiHvLI04nOrBo0lezs/GVUY5IS4PekUBE3aIvg1yOtPMJhADq342DgI0zsorEFzcOsDkZJ+IGZ/mnhE X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: bot+bpf-ci@kernel.org writes: > ``` > commit 712137918bba1b0a9c7c670bab9200b0f0d6a7e8 > Author: Roman Gushchin > > bpf: selftests: introduce read_cgroup_file() helper > > This patch adds a new helper function read_cgroup_file() to read from > cgroup control files in BPF selftests. The function opens a file, > reads into a buffer, and returns the result. > >> diff --git a/tools/testing/selftests/bpf/cgroup_helpers.c b/tools/testing/selftests/bpf/cgroup_helpers.c >> index 20cede4db..8fb02fe4c 100644 >> --- a/tools/testing/selftests/bpf/cgroup_helpers.c >> +++ b/tools/testing/selftests/bpf/cgroup_helpers.c >> @@ -126,6 +126,45 @@ int enable_controllers(const char *relative_path, const char *controllers) >> return __enable_controllers(cgroup_path, controllers); >> } >> >> +static size_t __read_cgroup_file(const char *cgroup_path, const char *file, >> + char *buf, size_t size) >> +{ >> + char file_path[PATH_MAX + 1]; >> + size_t ret; >> + int fd; >> + >> + snprintf(file_path, sizeof(file_path), "%s/%s", cgroup_path, file); >> + fd = open(file_path, O_RDONLY); >> + if (fd < 0) { >> + log_err("Opening %s", file_path); >> + return -1; > > Can __read_cgroup_file() return -1 when its return type is size_t? > > The function signature declares size_t (unsigned), but returns -1 here. > When -1 is implicitly converted to size_t, it becomes SIZE_MAX > (18446744073709551615 on 64-bit systems). Callers checking for errors > with "if (ret < 0)" will fail because size_t is unsigned, and callers > checking "if (ret == -1)" will also fail after the cast. > >> + } >> + >> + ret = read(fd, buf, size); >> + close(fd); >> + return ret; > > Does this handle read() errors correctly? > > The read() syscall returns ssize_t which can be negative on error. > Assigning this to size_t (line 143) converts negative error codes into > large positive numbers. For example, read() returning -1 becomes SIZE_MAX > when stored in ret. > > Should the return type be ssize_t instead of size_t to properly propagate > both success (byte count) and error (negative values) to callers? Correct, fixed to ssize_t. Thanks!