Re: [PATCH] proc: avoid leaking eip, esp, or wchan to non-privileged processes (fwd)

[Eric W. Biederman]

James Morris <jmorris@xxxxxxxxx> writes:

> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index aa763ab..cd3c0d7 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -319,6 +319,9 @@ static int proc_pid_wchan(struct task_struct *task, char
> *buffer)
>  	unsigned long wchan;
>  	char symname[KSYM_NAME_LEN];
>
> +	if (!ptrace_may_access(task, PTRACE_MODE_READ))
> +		return 0;
> +
>  	wchan = get_wchan(task);
>
>  	if (lookup_symbol_name(wchan, symname) < 0)

If the symbol is in the kernel it should be safe to return it's
name, all that is an information leak of a different sort.
Overall I expect we should return  -EPERM here and not simply
an empty file.

Have you tested these patches against ps top and similar common
tools?

Eric
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