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 <[email protected]>
The change ifself looks good:
Reviewed-by: Nam Cao <[email protected]>
