[Patch v3 3/6] 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>
Acked-by: Namhyung Kim <namhyung@kernel.org>
---
 tools/perf/builtin-kvm.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
index 9813f1eb56f9..d297a7b2c088 100644
--- a/tools/perf/builtin-kvm.c
+++ b/tools/perf/builtin-kvm.c
@@ -2008,11 +2008,12 @@ 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;
+	/*
+	 * Besides the 2 more options "-o" and "filename",
+	 * kvm_add_default_arch_event() may add 2 extra options,
+	 * so allocate 4 more items.
+	 */
+	rec_argc = argc + 2 + 2;
 	rec_argv = calloc(rec_argc + 1, sizeof(char *));
 	if (!rec_argv)
 		return -ENOMEM;
@@ -2025,6 +2026,10 @@ 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)
+		goto EXIT;
+
 	ret = cmd_record(i, rec_argv);
 
 EXIT:
-- 
2.34.1