Re: [PATCH v3 06/17] rv: Use strings in da monitors tracepoints

[Nam Cao <namcao@linutronix.de>]

On Tue, Jul 15, 2025 at 09:14:23AM +0200, Gabriele Monaco wrote:
> Using DA monitors tracepoints with KASAN enabled triggers the following
> warning:
> 
>  BUG: KASAN: global-out-of-bounds in do_trace_event_raw_event_event_da_monitor+0xd6/0x1a0
>  Read of size 32 at addr ffffffffaada8980 by task ...
>  Call Trace:
>   <TASK>
>  [...]
>   do_trace_event_raw_event_event_da_monitor+0xd6/0x1a0
>   ? __pfx_do_trace_event_raw_event_event_da_monitor+0x10/0x10
>   ? trace_event_sncid+0x83/0x200
>   trace_event_sncid+0x163/0x200
>  [...]
>  The buggy address belongs to the variable:
>   automaton_snep+0x4e0/0x5e0
> 
> This is caused by the tracepoints reading 32 bits __array instead of
                                               ^
                                               bytes

> __string from the automata definition. Such strings are literals and
> reading 32 bytes ends up in out of bound memory accesses (e.g. the next
> automaton's data in this case).
> The error is harmless as, while printing the string, we stop at the null
> terminator, but it should still be fixed.

I'm not sure about the "harmless" part. What if this string is at the very
end of kernel image? Wouldn't unmapped memory be read?

> Use the __string facilities while defining the tracepoints to avoid
> reading out of bound memory.
> 
> Fixes: 792575348ff7 ("rv/include: Add deterministic automata monitor definition via C macros")
> Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>

The change ifself looks good:

Reviewed-by: Nam Cao <namcao@linutronix.de>