Messages in this thread Patch in this message | | | From | Cong Wang <> | Subject | [Patch v2] proc: clean up /proc/<pid>/environ handling | Date | Tue, 3 Apr 2012 16:28:13 +0800 |
| |
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.
Signed-off-by: WANG Cong <xiyou.wangcong@gmail.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> --- fs/proc/base.c | 65 +++++++++++++++++++++++++++++++++++++++---------------- 1 files changed, 46 insertions(+), 19 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c index 1c8b280..b863ba3 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -801,30 +801,50 @@ 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 (IS_ERR(mm)) + return PTR_ERR(mm); + + if (mm) { + /* ensure this mm_struct can't be freed */ + atomic_inc(&mm->mm_count); + /* but do not pin its memory */ + mmput(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; + 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 +856,7 @@ 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 +875,26 @@ 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 int environ_release(struct inode *inode, struct file *file) +{ + struct mm_struct *mm = file->private_data; + if (mm) + mmdrop(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,
| |