Hi Steve,
Steven Rostedt <rostedt@xxxxxxxxxxx> writes:
> From: Steven Rostedt <rostedt@xxxxxxxxxxx>
>
> Pingfan reported that the following causes a fault:
>
> echo "filename ~ \"cpu\"" > events/syscalls/sys_enter_openat/filter
> echo 1 > events/syscalls/sys_enter_at/enable
>
[..]
> +static __always_inline char *test_string(char *str)
> +{
> + struct ustring_buffer *ubuf;
> + char __user *ustr;
> + char *kstr;
> +
> + if (!ustring_per_cpu)
> + return NULL;
> +
> + ubuf = this_cpu_ptr(ustring_per_cpu);
> + kstr = ubuf->buffer;
> +
> + if (likely((unsigned long)str >= TASK_SIZE)) {
I think that would not work on architectures where addresses for kernel
and user space could overlap, i.e. with different address spaces?
> + /* For safety, do not trust the string pointer */
> + if (!strncpy_from_kernel_nofault(kstr, str, USTRING_BUF_SIZE))
> + return NULL;
> + } else {
> + /* user space address? */
> + ustr = str;
> + if (!strncpy_from_user_nofault(kstr, ustr, USTRING_BUF_SIZE))
> + return NULL;
> + }
> + return kstr;
> +}
