Re: [PATCH v1 05/11] perf trace: Smatch: Fix potential NULL pointer dereference

[Arnaldo Carvalho de Melo]

Em Tue, Jul 02, 2019 at 06:34:14PM +0800, Leo Yan escreveu:
> Based on the following report from Smatch, fix the potential
> NULL pointer dereference check.
> 
>   tools/perf/builtin-trace.c:1044
>   thread_trace__new() error: we previously assumed 'ttrace' could be
>   null (see line 1041).
> 
> tools/perf/builtin-trace.c
> 1037 static struct thread_trace *thread_trace__new(void)
> 1038 {
> 1039         struct thread_trace *ttrace =  zalloc(sizeof(struct thread_trace));
> 1040
> 1041         if (ttrace)
> 1042                 ttrace->files.max = -1;
> 1043
> 1044         ttrace->syscall_stats = intlist__new(NULL);
>              ^^^^^^^^
> 1045
> 1046         return ttrace;
> 1047 }
> 
> This patch directly returns NULL when fail to allocate memory for
> ttrace; this can avoid potential NULL pointer dereference.

I did it slightly different, to avoid having two return lines, and that
is what most other constructors (foo__new()) do in tools/perf/, kept
your changeset comment and patch authorship, thanks.

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index d0eb7224dd36..e3fc9062f136 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -1038,10 +1038,10 @@ static struct thread_trace *thread_trace__new(void)
 {
 	struct thread_trace *ttrace =  zalloc(sizeof(struct thread_trace));
 
-	if (ttrace)
+	if (ttrace) {
 		ttrace->files.max = -1;
-
-	ttrace->syscall_stats = intlist__new(NULL);
+		ttrace->syscall_stats = intlist__new(NULL);
+	}
 
 	return ttrace;
 }