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

Similar to e268337dfe26 ("proc: clean up and fix /proc/<pid>/mem
handling"), move the check of permission to open(), this will simplify
read() code.

[akpm@linux-foundation.org: checkpatch fixes]
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 24 insertions, 21 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index d7d711876b6a..e2d234243269 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -679,7 +679,7 @@ static const struct file_operations proc_single_file_operations = {
         .release        = single_release,
 };
 
-static int mem_open(struct inode* inode, struct file* file)
+static int __mem_open(struct inode *inode, struct file *file, unsigned int mode)
 {
         struct task_struct *task = get_proc_task(file->f_path.dentry->d_inode);
         struct mm_struct *mm;
@@ -687,7 +687,7 @@ static int mem_open(struct inode* inode, struct file* file)
         if (!task)
                 return -ESRCH;
 
-        mm = mm_access(task, PTRACE_MODE_ATTACH);
+        mm = mm_access(task, mode);
         put_task_struct(task);
 
         if (IS_ERR(mm))
@@ -707,6 +707,11 @@ static int mem_open(struct inode* inode, struct file* file)
         return 0;
 }
 
+static int mem_open(struct inode *inode, struct file *file)
+{
+        return __mem_open(inode, file, PTRACE_MODE_ATTACH);
+}
+
 static ssize_t mem_rw(struct file *file, char __user *buf,
                         size_t count, loff_t *ppos, int write)
 {
@@ -803,30 +808,29 @@ static const struct file_operations proc_mem_operations = {
         .release        = mem_release,
 };
 
+static int environ_open(struct inode *inode, struct file *file)
+{
+        return __mem_open(inode, file, PTRACE_MODE_READ);
+}
+
 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;
+        int ret = 0;
+        struct mm_struct *mm = file->private_data;
 
-        if (!task)
-                goto out_no_task;
+        if (!mm)
+                return 0;
 
-        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;
+        if (!atomic_inc_not_zero(&mm->mm_users))
+                goto free;
         while (count > 0) {
                 int this_len, retval, max_len;
 
@@ -838,7 +842,7 @@ 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) {
@@ -857,19 +861,18 @@ static ssize_t environ_read(struct file *file, char __user *buf,
                 count -= retval;
         }
         *ppos = src;
-
         mmput(mm);
-out_free:
+
+free:
         free_page((unsigned long) page);
-out:
-        put_task_struct(task);
-out_no_task:
         return ret;
 }
 
 static const struct file_operations proc_environ_operations = {
+        .open           = environ_open,
         .read           = environ_read,
         .llseek         = generic_file_llseek,
+        .release        = mem_release,
 };
 
 static ssize_t oom_adjust_read(struct file *file, char __user *buf,