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Date:   Tue, 18 Aug 2020 13:39:44 +0800
From:   kernel test robot <lkp@...el.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        linux-kernel@...r.kernel.org
Cc:     kbuild-all@...ts.01.org, linux-fsdevel@...r.kernel.org,
        criu@...nvz.org, bpf@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Jann Horn <jann@...jh.net>, Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH 11/17] bpf/task_iter: In task_file_seq_get_next use
 fnext_task

Hi "Eric,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on bpf/master]
[also build test WARNING on linus/master v5.9-rc1 next-20200817]
[cannot apply to bpf-next/master linux/master]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Eric-W-Biederman/exec-Move-unshare_files-to-fix-posix-file-locking-during-exec/20200818-061552
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git master
config: i386-randconfig-m021-20200818 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@...el.com>

smatch warnings:
kernel/bpf/task_iter.c:162 task_file_seq_get_next() warn: ignoring unreachable code.

# https://github.com/0day-ci/linux/commit/66f80aa453b17f8932b42e18265dba5fdb32490e
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Eric-W-Biederman/exec-Move-unshare_files-to-fix-posix-file-locking-during-exec/20200818-061552
git checkout 66f80aa453b17f8932b42e18265dba5fdb32490e
vim +162 kernel/bpf/task_iter.c

   128	
   129	static struct file *
   130	task_file_seq_get_next(struct bpf_iter_seq_task_file_info *info,
   131			       struct task_struct **task)
   132	{
   133		struct pid_namespace *ns = info->common.ns;
   134		u32 curr_tid = info->tid;
   135		struct task_struct *curr_task;
   136		unsigned int curr_fd = info->fd;
   137	
   138		/* If this function returns a non-NULL file object,
   139		 * it held a reference to the task/file.
   140		 * Otherwise, it does not hold any reference.
   141		 */
   142	again:
   143		if (*task) {
   144			curr_task = *task;
   145			curr_fd = info->fd;
   146		} else {
   147			curr_task = task_seq_get_next(ns, &curr_tid);
   148			if (!curr_task)
   149				return NULL;
   150	
   151			/* set *task and info->tid */
   152			*task = curr_task;
   153			if (curr_tid == info->tid) {
   154				curr_fd = info->fd;
   155			} else {
   156				info->tid = curr_tid;
   157				curr_fd = 0;
   158			}
   159		}
   160	
   161		rcu_read_lock();
 > 162		for (;; curr_fd++) {
   163			struct file *f;
   164	
   165			f = fnext_task(curr_task, &curr_fd);
   166			if (!f)
   167				break;
   168	
   169			/* set info->fd */
   170			info->fd = curr_fd;
   171			get_file(f);
   172			rcu_read_unlock();
   173			return f;
   174		}
   175	
   176		/* the current task is done, go to the next task */
   177		rcu_read_unlock();
   178		put_task_struct(curr_task);
   179		*task = NULL;
   180		info->fd = 0;
   181		curr_tid = ++(info->tid);
   182		goto again;
   183	}
   184	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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