[PATCH 2/5] perf tools kvm: Fix the potential out of range memory access issue

[Dapeng Mi <dapeng1.mi@linux.intel.com>]

kvm_add_default_arch_event() helper may add 2 extra options but it
directly modifies the original argv[] array. This may cause out of range
memory access. Fix this issue.

Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
---
 tools/perf/builtin-kvm.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
index f78a67a199ff..7e48d2437710 100644
--- a/tools/perf/builtin-kvm.c
+++ b/tools/perf/builtin-kvm.c
@@ -2002,12 +2002,12 @@ static int __cmd_record(const char *file_name, int argc, const char **argv)
 	int rec_argc, i = 0, j, ret;
 	const char **rec_argv;
 
-	ret = kvm_add_default_arch_event(&argc, argv);
-	if (ret)
-		return -EINVAL;
-
 	rec_argc = argc + 2;
-	rec_argv = calloc(rec_argc + 1, sizeof(char *));
+	/*
+	 * kvm_add_default_arch_event() may add 2 extra options, so
+	 * allocate 2 more pointers in adavance.
+	 */
+	rec_argv = calloc(rec_argc + 2 + 1, sizeof(char *));
 	if (!rec_argv)
 		return -ENOMEM;
 
@@ -2019,6 +2019,10 @@ static int __cmd_record(const char *file_name, int argc, const char **argv)
 
 	BUG_ON(i != rec_argc);
 
+	ret = kvm_add_default_arch_event(&i, rec_argv);
+	if (ret)
+		return -EINVAL;
+
 	ret = cmd_record(i, rec_argv);
 	free(rec_argv);
 	return ret;
-- 
2.34.1