proc: clean up /proc/<pid>/environ handling

Similar to e268337dfe2 ("proc: clean up and fix /proc/<pid>/mem
handling"), move the check of permission to open(), this will simplify
read() code.

Signed-off-by: WANG Cong <xiyou.wangcong@gmail.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 1c8b280146d7a0956dddd1f06e431f49671bd269..db33f3b268bc6708a5c7a15e4cd1259ffc8524ba 100644 (file)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -801,28 +801,38 @@ static const struct file_operations proc_mem_operations = {
        .release        = mem_release,
 };
 
+static int environ_open(struct inode *inode, struct file *file)
+{
+       struct task_struct *task = get_proc_task(file->f_path.dentry->d_inode);
+       struct mm_struct *mm;
+
+       if (!task)
+               return -ESRCH;
+
+       mm = mm_for_maps(task);
+       put_task_struct(task);
+
+       if (!mm)
+               return -ENOENT;
+       if (IS_ERR(mm))
+               return PTR_ERR(mm);
+
+       file->private_data = mm;
+
+       return 0;
+}
+
 static ssize_t environ_read(struct file *file, char __user *buf,
                        size_t count, loff_t *ppos)
 {
-       struct task_struct *task = get_proc_task(file->f_dentry->d_inode);
        char *page;
        unsigned long src = *ppos;
-       int ret = -ESRCH;
-       struct mm_struct *mm;
-
-       if (!task)
-               goto out_no_task;
+       int ret = 0;
+       struct mm_struct *mm = file->private_data;
 
-       ret = -ENOMEM;
        page = (char *)__get_free_page(GFP_TEMPORARY);
        if (!page)
-               goto out;
-
-
-       mm = mm_for_maps(task);
-       ret = PTR_ERR(mm);
-       if (!mm || IS_ERR(mm))
-               goto out_free;
+               return -ENOMEM;
 
        ret = 0;
        while (count > 0) {
@@ -836,7 +846,7 @@ static ssize_t environ_read(struct file *file, char __user *buf,
                max_len = (count > PAGE_SIZE) ? PAGE_SIZE : count;
                this_len = (this_len > max_len) ? max_len : this_len;
 
-               retval = access_process_vm(task, (mm->env_start + src),
+               retval = access_remote_vm(mm, (mm->env_start + src),
                        page, this_len, 0);
 
                if (retval <= 0) {
@@ -856,18 +866,23 @@ static ssize_t environ_read(struct file *file, char __user *buf,
        }
        *ppos = src;
 
-       mmput(mm);
-out_free:
        free_page((unsigned long) page);
-out:
-       put_task_struct(task);
-out_no_task:
        return ret;
 }
 
+static int environ_release(struct inode *inode, struct file *file)
+{
+       struct mm_struct *mm = file->private_data;
+
+       mmput(mm);
+       return 0;
+}
+
 static const struct file_operations proc_environ_operations = {
+       .open           = environ_open,
        .read           = environ_read,
        .llseek         = generic_file_llseek,
+       .release        = environ_release,
 };
 
 static ssize_t oom_adjust_read(struct file *file, char __user *buf,