Re: [PATCH v2] tracing: replace multiple deprecated strncpy with memcpy

[Steven Rostedt]

On Mon, 14 Oct 2024 14:31:29 -0700
Kees Cook <kees@xxxxxxxxxx> wrote:
> 
> We know the destination must have a NUL-terminated string. Is the src
> NUL terminated? Looking at parse_pred(), it seems like no? And we can't
> use memtostr_pad() here because the source buffer size isn't known at
> compile time. Okay then. And there are no NUL bytes in the "str + s"
> span, so yeah, it looks like memcpy() is best.
> 
> Reviewed-by: Kees Cook <kees@xxxxxxxxxx>
> 

The code is simply breaking up parts of one string and copying the bits
into other strings. Like the example that broke:

$ echo 'common_pid != 0 && common_pid != 120 && common_pid != 1253 &&
  common_pid != 17 && common_pid != 394 && common_pid != 81 &&
  common_pid != 87' > /sys/kernel/tracing/events/sched/sched_switch/filter

It would need to move each of the above tokens "common_pid", "!=", "0", "&&", etc
into their own strings for later processing. The parser finds the start and
end of the location needed to copy, so memcpy() followed by a nul byte is fine.

-- Steve