On Sun, Mar 11, 2012 at 12:25:18AM +0100, Djalal Harouni wrote:
> The /proc/<pid>/{environ,pagemap} are sensitive files which must be
> protected across execve to avoid information leaks.
>
> These files are protected by attaching them to their task at open time by
> saving the exec_id of the target task, this way in read we just compare
> the target task's exec_id and the previously saved exec_id of the
> proc_file_private struct, in other words we just bind these files to their
> appropriate process image at open time. We do this since we are able to do
> proper permission checks (ptrace) at each syscall, so we do not care about
> the reader.
>
> Another important rule is to set the exec_id of the target task before the
> permission checks at open, this way we do not race against target task
> execve, and it will be more effective if the exec_id check at read/write
> times are delayed as much as possible to be sure that the target task do
> not change during execve.
>
> This patch adds the open file_operation to the
> /proc/<pid>/{environ,pagemap} so we are able to set the exec_id of the
> target task and to do the appropriate permission checks. The exec_id check
> is done in the related read file_operation.
->open is duplicated.
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> +static int environ_open(struct inode *inode, struct file *filp)
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