[PATCH 1/6 v3] proc: clean up /proc//environ handling

V3: Unify environ_open with mem_open(), and mem_release() too
V2: Add similar fix with 6d08f2c7139790c268820a2e590795cb8333181a
"proc: make sure mem_open() doesn't pin the target's memory",
suggested by Oleg.

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

Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>

fs/proc/base.c | 45 ++++++++++++++++++++++++
1 files changed, 24 insertions(+), 21 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 1c8b280..f3c4887 100644
a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -677,7 +677,7 @@ 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;
@@ -685,7 +685,7 @@ 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))
@@ -705,6 +705,11 @@ 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)
{
@@ -801,30 +806,29 @@ 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;

@@ -836,7 +840,7 @@ 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) {
@@ -855,19 +859,18 @@ 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,
1.7.7.6

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