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>

diff --git a/fs/proc/base.c b/fs/proc/base.c
index d7d711876b6a00e8bf3ba659db8f59d69d6862dc..e2d234243269555b6e52087a0e358e2522451906 100644 (file)
--- 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,