rtla/timerlat: Add bounds check for softirq vector

Add bounds checking when accessing the softirq_name array using the
vector value from kernel trace data. The vector field from the
osnoise:softirq_noise event is used directly as an array index without
validation, which could cause an out-of-bounds read if the kernel
provides an unexpected vector value.

The softirq_name array contains 10 elements corresponding to the
standard Linux softirq vectors. While the kernel should only provide
valid vector values in the range 0-9, defensive programming requires
validating untrusted input before using it as an array index. If an
out-of-range vector is encountered, display the word UNKNOWN instead
of attempting to read beyond the array bounds.

Signed-off-by: Wander Lairson Costa <wander@redhat.com>
Link: https://lore.kernel.org/r/20260309195040.1019085-9-wander@redhat.com
Signed-off-by: Tomas Glozar <tglozar@redhat.com>

Author: walac

tools/tracing/rtla/src/timerlat_aa.c

@@ -417,8 +417,8 @@ static int timerlat_aa_softirq_handler(struct trace_seq *s, struct tep_record *r
 	taa_data->thread_softirq_sum += duration;
 
 	trace_seq_printf(taa_data->softirqs_seq, "  %24s:%-3llu %.*s %9.2f us\n",
-			 softirq_name[vector], vector,
-			 24, spaces,
+			 vector < ARRAY_SIZE(softirq_name) ? softirq_name[vector] : "UNKNOWN",
+			 vector, 24, spaces,
 			 ns_to_usf(duration));
 	return 0;
 }