From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oi1-f176.google.com (mail-oi1-f176.google.com [209.85.167.176]) (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 D43902C9C for ; Mon, 31 Jan 2022 17:56:20 +0000 (UTC) Received: by mail-oi1-f176.google.com with SMTP id e81so28173039oia.6 for ; Mon, 31 Jan 2022 09:56:20 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=usp.br; s=usp-google; h=date:from:to:cc:subject:message-id:mime-version:content-disposition :content-transfer-encoding; bh=BVD0NSbX3nj02sBgzS26Hzi8d1ZIOHSSU47jm/3MiI0=; b=kEM6rNetZF01SR0pi5B+qDDKi3p/QNb3xolAKlDE3PbprwbOww1d0ZRLalVqU9fwHY 1kKtnwvoE65sHCs7JX+ZVlBmfLYE4sslG9hvPFVcL104Gy/BhEQd+zKVCXZppeg4xMUe 3wh4tKonjg/Zp7Qm9yrxLgQzZ3i575Hj5ddAai/sxziVCoaVs8cEl1my7e0R0TWl4EdV GBlDZX6fxsr3P33VRf0nN1pGgqVQK9uJLFdzVeOlxjzvPfNBKXHPlaEZ9Zz0nAuzp/q5 ICqxDNCecVtvhOx8QLvMJTu26eovXTbxs/0HflbKs4Tf8qIaYjw30c8LFME3hXPs5mOB VmaQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:mime-version :content-disposition:content-transfer-encoding; bh=BVD0NSbX3nj02sBgzS26Hzi8d1ZIOHSSU47jm/3MiI0=; b=bDLzZt2OuAPjB2jRWLhPP/0EaaJh2PwSGipZmH1OAg6m/GIqcX+cxQ++L4fP5kwwPk p4Jtg8P1cmB0Ujq4Rrp5i3Ai8sDnN/HZJWxSWSY5n99L3yoKFLEJn8aNNshdqMN6JKP/ GTbJYd3rEWBV3zNJHKbUvsnTcxs+uSfsBN5Oit5tlS1LB0e3rwdKA8hcX4dzDuhHY9Hi pbTgcEb9ZsRLUiaooK9RjuPghUdd9exhEG8KsYH72gmQE+yViqAzEzKwkSvzir8oaX7J QQItKV4WEv4SmfVsXvezHX+6ExxmlarY8vxskcNdotFBoA1ujxbkOfTATnPtBU0Sxb0v EngQ== X-Gm-Message-State: AOAM5316UwgCkYCNLS7nsGItTxCdByFJdCA15zH/4JX/TPPNjNvZlFrP WBj2VtyepKdJqu7yO7T3TPOAog== X-Google-Smtp-Source: ABdhPJxTt13DSu5K/UgSNfsHqPrBctZ8yNK463AzxV13RIocT8h2aaYGcoAZcFFPegFyhHACuSBw/Q== X-Received: by 2002:a05:6808:1583:: with SMTP id t3mr18106273oiw.248.1643651779818; Mon, 31 Jan 2022 09:56:19 -0800 (PST) Received: from fedora ([187.36.236.204]) by smtp.gmail.com with ESMTPSA id w191sm13425965oiw.42.2022.01.31.09.56.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 31 Jan 2022 09:56:19 -0800 (PST) Date: Mon, 31 Jan 2022 14:56:13 -0300 From: =?iso-8859-1?Q?Ma=EDra?= Canal To: gregkh@linuxfoundation.org, tj@kernel.org, viro@zeniv.linux.org.uk, nathan@kernel.org, ndesaulniers@google.com Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, llvm@lists.linux.dev Subject: [PATCH v2] seq_file: fix NULL pointer arithmetic warning Message-ID: Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit Implement conditional logic in order to replace NULL pointer arithmetic. The use of NULL pointer arithmetic was pointed out by clang with the following warning: fs/kernfs/file.c:128:15: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] return NULL + !*ppos; ~~~~ ^ fs/seq_file.c:559:14: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] return NULL + (*pos == 0); Signed-off-by: Maíra Canal --- V1 -> V2: - Use SEQ_START_TOKEN instead of open-coding it - kernfs_seq_start call single_start instead of open-coding it --- fs/kernfs/file.c | 7 +------ fs/seq_file.c | 5 +++-- include/linux/seq_file.h | 1 + 3 files changed, 5 insertions(+), 8 deletions(-) diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c index 9414a7a60a9f..7aefaca876a0 100644 --- a/fs/kernfs/file.c +++ b/fs/kernfs/file.c @@ -120,13 +120,8 @@ static void *kernfs_seq_start(struct seq_file *sf, loff_t *ppos) if (next == ERR_PTR(-ENODEV)) kernfs_seq_stop_active(sf, next); return next; - } else { - /* - * The same behavior and code as single_open(). Returns - * !NULL if pos is at the beginning; otherwise, NULL. - */ - return NULL + !*ppos; } + return single_start(sf, ppos); } static void *kernfs_seq_next(struct seq_file *sf, void *v, loff_t *ppos) diff --git a/fs/seq_file.c b/fs/seq_file.c index f8e1f4ee87ff..bb2b15d3f1c5 100644 --- a/fs/seq_file.c +++ b/fs/seq_file.c @@ -554,10 +554,11 @@ int seq_dentry(struct seq_file *m, struct dentry *dentry, const char *esc) } EXPORT_SYMBOL(seq_dentry); -static void *single_start(struct seq_file *p, loff_t *pos) +void *single_start(struct seq_file *p, loff_t *pos) { - return NULL + (*pos == 0); + return *pos ? NULL : SEQ_START_TOKEN; } +EXPORT_SYMBOL(single_start); static void *single_next(struct seq_file *p, void *v, loff_t *pos) { diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h index 88cc16444b43..60820ab511d2 100644 --- a/include/linux/seq_file.h +++ b/include/linux/seq_file.h @@ -162,6 +162,7 @@ int seq_dentry(struct seq_file *, struct dentry *, const char *); int seq_path_root(struct seq_file *m, const struct path *path, const struct path *root, const char *esc); +void *single_start(struct seq_file *, loff_t *); int single_open(struct file *, int (*)(struct seq_file *, void *), void *); int single_open_size(struct file *, int (*)(struct seq_file *, void *), void *, size_t); int single_release(struct inode *, struct file *); -- 2.34.1