[PATCH] samples/seccomp: improve label helper

[Kees Cook]

Fixes a potential corruption with uninitialized stack memory in the seccomp
BPF sample program.

Reported-by: Robert Swiecki <swiecki@xxxxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
 samples/seccomp/bpf-fancy.c  | 4 +++-
 samples/seccomp/bpf-helper.c | 5 +++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/samples/seccomp/bpf-fancy.c b/samples/seccomp/bpf-fancy.c
index 8eb483aaec46..e8b24f443709 100644
--- a/samples/seccomp/bpf-fancy.c
+++ b/samples/seccomp/bpf-fancy.c
@@ -25,7 +25,9 @@
 
 int main(int argc, char **argv)
 {
-	struct bpf_labels l;
+	struct bpf_labels l = {
+		.count = 0,
+	};
 	static const char msg1[] = "Please type something: ";
 	static const char msg2[] = "You typed: ";
 	char buf[256];
diff --git a/samples/seccomp/bpf-helper.c b/samples/seccomp/bpf-helper.c
index 579cfe331886..f9fa14d81798 100644
--- a/samples/seccomp/bpf-helper.c
+++ b/samples/seccomp/bpf-helper.c
@@ -10,6 +10,7 @@
  */
 
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 
 #include "bpf-helper.h"
@@ -63,6 +64,10 @@ __u32 seccomp_bpf_label(struct bpf_labels *labels, const char *label)
 {
 	struct __bpf_label *begin = labels->labels, *end;
 	int id;
+	if (labels->count == BPF_LABELS_MAX) {
+		fprintf(stderr, "Too many labels\n");
+		exit(1);
+	}
 	if (labels->count == 0) {
 		begin->label = label;
 		begin->location = 0xffffffff;
-- 
1.9.1


-- 
Kees Cook
Chrome OS Security
--
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