Re: [RFC PATCH net-next] bpf: fix potential percpu map overcopy to user.

On 10/20/2016 08:41 PM, William Tu wrote:

On Thu, Oct 20, 2016 at 9:58 AM, Alexei Starovoitov
[off-list ref] wrote:

quoted

On Thu, Oct 20, 2016 at 06:04:38PM +0200, Daniel Borkmann wrote:

quoted

diff --git a/tools/testing/selftests/bpf/test_maps.c b/tools/testing/selftests/bpf/test_maps.c
index ee384f0..d4832e8 100644
--- a/tools/testing/selftests/bpf/test_maps.c
+++ b/tools/testing/selftests/bpf/test_maps.c

@@ -25,6 +25,33 @@

  static int map_flags;

+static unsigned int num_possible_cpus(void)
+{
+     static const char *fcpu = "/sys/devices/system/cpu/possible";
+     unsigned int val, possible_cpus = 0;
+     char buff[128];
+     FILE *fp;
+
+     fp = fopen(fcpu, "r");
+     if (!fp) {
+             printf("Failed to open %s: '%s'!\n", fcpu, strerror(errno));
+             exit(1);
+     }
+
+     while (fgets(buff, sizeof(buff), fp)) {
+             if (sscanf(buff, "%*u-%u", &val) == 1)
+                     possible_cpus = val;
+     }

looks great to me.
Could you move it into bpf_sys.h or somehow make it common in libbpf
and reuse it in samples/bpf/ ?
Since quite a few samples need this fix as well.

Ahh, true.

quoted

Thanks!

Looks good to me. I tested it and it works fine.

Okay, thanks. I'll fix that up, mid-term we should try and move most of
that over to kernel selftests/bpf, and reuse tools/lib/bpf/.

Thanks!
William