[PATCH 6.1 243/609] tracing/probes: Prevent out-of-bounds write in __trace_probe_log_err()

6.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Masami Hiramatsu (Google) <[email protected]>

commit a9d6fb284039a5d3858a1d9f9a0d7e46cfb7c2d4 upstream.

If trace_probe_log.argc is 0 in __trace_probe_log_err(), the loop
constructing the command string will not execute and p will remain equal to
command. Writing to *(p - 1) will cause an out-of-bounds access before
command. This should not happen, but better to be treated.

Reject if trace_probe_log.argc is 0.

Link: https://lore.kernel.org/all/178454233992.290363.18323091580600697731.stgit@devnote2/

Fixes: ab105a4fb894 ("tracing: Use tracing error_log with probe events")
Cc: [email protected]
Assisted-by: Antigravity:gemini-3.5-flash
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
 kernel/trace/trace_probe.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -176,7 +176,7 @@ void __trace_probe_log_err(int offset, i
 
 	lockdep_assert_held(&dyn_event_ops_mutex);
 
-	if (!trace_probe_log.argv)
+	if (!trace_probe_log.argv || !trace_probe_log.argc)
 		return;
 
 	/* Recalculate the length and allocate buffer */