mm: kfence: fix elapsed time for allocated/freed track

Fix elapsed time for the allocated/freed track introduced by commit
62e73fd8.

Link: https://lkml.kernel.org/r/20240924085004.75401-1-qiwu.chen@transsion.com
Fixes: 62e73fd8 ("mm: kfence: print the elapsed time for allocated/freed track")
Signed-off-by: qiwu.chen <qiwu.chen@transsion.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/kfence/report.c

@@ -109,7 +109,7 @@ static void kfence_print_stack(struct seq_file *seq, const struct kfence_metadat
 	const struct kfence_track *track = show_alloc ? &meta->alloc_track : &meta->free_track;
 	u64 ts_sec = track->ts_nsec;
 	unsigned long rem_nsec = do_div(ts_sec, NSEC_PER_SEC);
-	u64 interval_nsec = local_clock() - meta->alloc_track.ts_nsec;
+	u64 interval_nsec = local_clock() - track->ts_nsec;
 	unsigned long rem_interval_nsec = do_div(interval_nsec, NSEC_PER_SEC);
 
 	/* Timestamp matches printk timestamp format. */