From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:57026 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S939457AbcIVRoG (ORCPT ); Thu, 22 Sep 2016 13:44:06 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Mateusz Guzik , Konstantin Khlebnikov , Richard Guy Briggs , Paul Moore Subject: [PATCH 4.7 054/184] mm: introduce get_task_exe_file Date: Thu, 22 Sep 2016 19:39:48 +0200 Message-Id: <20160922174051.020179076@linuxfoundation.org> In-Reply-To: <20160922174048.653794923@linuxfoundation.org> References: <20160922174048.653794923@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.7-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mateusz Guzik commit cd81a9170e69e018bbaba547c1fd85a585f5697a upstream. For more convenient access if one has a pointer to the task. As a minor nit take advantage of the fact that only task lock + rcu are needed to safely grab ->exe_file. This saves mm refcount dance. Use the helper in proc_exe_link. Signed-off-by: Mateusz Guzik Acked-by: Konstantin Khlebnikov Acked-by: Richard Guy Briggs Signed-off-by: Paul Moore Signed-off-by: Greg Kroah-Hartman --- fs/proc/base.c | 7 +------ include/linux/mm.h | 1 + kernel/fork.c | 23 +++++++++++++++++++++++ 3 files changed, 25 insertions(+), 6 deletions(-) --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -1552,18 +1552,13 @@ static const struct file_operations proc static int proc_exe_link(struct dentry *dentry, struct path *exe_path) { struct task_struct *task; - struct mm_struct *mm; struct file *exe_file; task = get_proc_task(d_inode(dentry)); if (!task) return -ENOENT; - mm = get_task_mm(task); + exe_file = get_task_exe_file(task); put_task_struct(task); - if (!mm) - return -ENOENT; - exe_file = get_mm_exe_file(mm); - mmput(mm); if (exe_file) { *exe_path = exe_file->f_path; path_get(&exe_file->f_path); --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1975,6 +1975,7 @@ extern void mm_drop_all_locks(struct mm_ extern void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file); extern struct file *get_mm_exe_file(struct mm_struct *mm); +extern struct file *get_task_exe_file(struct task_struct *task); extern bool may_expand_vm(struct mm_struct *, vm_flags_t, unsigned long npages); extern void vm_stat_account(struct mm_struct *, vm_flags_t, long npages); --- a/kernel/fork.c +++ b/kernel/fork.c @@ -801,6 +801,29 @@ struct file *get_mm_exe_file(struct mm_s EXPORT_SYMBOL(get_mm_exe_file); /** + * get_task_exe_file - acquire a reference to the task's executable file + * + * Returns %NULL if task's mm (if any) has no associated executable file or + * this is a kernel thread with borrowed mm (see the comment above get_task_mm). + * User must release file via fput(). + */ +struct file *get_task_exe_file(struct task_struct *task) +{ + struct file *exe_file = NULL; + struct mm_struct *mm; + + task_lock(task); + mm = task->mm; + if (mm) { + if (!(task->flags & PF_KTHREAD)) + exe_file = get_mm_exe_file(mm); + } + task_unlock(task); + return exe_file; +} +EXPORT_SYMBOL(get_task_exe_file); + +/** * get_task_mm - acquire a reference to the task's mm * * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning