On Thu, Apr 6, 2017 at 4:56 PM, Akinobu Mita <akinobu.m...@gmail.com> wrote:
> The fail-nth file is created with 0666 and the access is permitted if
> and only if the task is current.
>
> This file is owned by the currnet user. So we can create it with 0644
> and allow the owner to write it. This enables to watch the status of
> task->fail_nth from another processes.
>
> Cc: Dmitry Vyukov <dvyu...@google.com>
> Signed-off-by: Akinobu Mita <akinobu.m...@gmail.com>
> ---
> fs/proc/base.c | 22 ++++++++--------------
> 1 file changed, 8 insertions(+), 14 deletions(-)
>
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index 9d14215..14e7b73 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -1366,16 +1366,16 @@ static ssize_t proc_fail_nth_write(struct file *file,
> const char __user *buf,
> int err;
> unsigned int n;
>
> + err = kstrtoint_from_user(buf, count, 0, &n);
/\/\/\/\/\
I think this should be kstrtouint_from_user. Otherwise it effective
reverts one of previous patches.
> + if (err)
> + return err;
> +
> task = get_proc_task(file_inode(file));
> if (!task)
> return -ESRCH;
> + task->fail_nth = n;
> put_task_struct(task);
> - if (task != current)
> - return -EPERM;
> - err = kstrtouint_from_user(buf, count, 0, &n);
> - if (err)
> - return err;
> - current->fail_nth = n;
> +
> return count;
> }
>
> @@ -1389,11 +1389,9 @@ static ssize_t proc_fail_nth_read(struct file *file,
> char __user *buf,
> task = get_proc_task(file_inode(file));
> if (!task)
> return -ESRCH;
> - put_task_struct(task);
> - if (task != current)
> - return -EPERM;
> len = snprintf(numbuf, sizeof(numbuf), "%u\n", task->fail_nth);
> len = simple_read_from_buffer(buf, count, ppos, numbuf, len);
> + put_task_struct(task);
>
> return len;
> }
> @@ -3358,11 +3356,7 @@ static const struct pid_entry tid_base_stuff[] = {
> #endif
> #ifdef CONFIG_FAULT_INJECTION
> REG("make-it-fail", S_IRUGO|S_IWUSR, proc_fault_inject_operations),
> - /*
> - * Operations on the file check that the task is current,
> - * so we create it with 0666 to support testing under unprivileged
> user.
> - */
> - REG("fail-nth", 0666, proc_fail_nth_operations),
> + REG("fail-nth", 0644, proc_fail_nth_operations),
> #endif
> #ifdef CONFIG_TASK_IO_ACCOUNTING
> ONE("io", S_IRUSR, proc_tid_io_accounting),
> --
> 2.7.4
>
