bpftool: Fix undefined behavior caused by shifting into the sign bit

Replace shifts of '1' with '1U' in bitwise operations within
__show_dev_tc_bpf() to prevent undefined behavior caused by shifting
into the sign bit of a signed integer. By using '1U', the operations
are explicitly performed on unsigned integers, avoiding potential
integer overflow or sign-related issues.

Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Quentin Monnet <qmo@kernel.org>
Link: https://lore.kernel.org/bpf/20240908140009.3149781-1-visitorckw@gmail.com

diff --git a/tools/bpf/bpftool/net.c b/tools/bpf/bpftool/net.c
index 2a51f1c..3c50fc6 100644 (file)
--- a/tools/bpf/bpftool/net.c
+++ b/tools/bpf/bpftool/net.c
@@ -486,9 +486,9 @@ static void __show_dev_tc_bpf(const struct ip_devname_ifindex *dev,
                if (prog_flags[i] || json_output) {
                        NET_START_ARRAY("prog_flags", "%s ");
                        for (j = 0; prog_flags[i] && j < 32; j++) {
-                               if (!(prog_flags[i] & (1 << j)))
+                               if (!(prog_flags[i] & (1U << j)))
                                        continue;
-                               NET_DUMP_UINT_ONLY(1 << j);
+                               NET_DUMP_UINT_ONLY(1U << j);
                        }
                        NET_END_ARRAY("");
                }
@@ -497,9 +497,9 @@ static void __show_dev_tc_bpf(const struct ip_devname_ifindex *dev,
                        if (link_flags[i] || json_output) {
                                NET_START_ARRAY("link_flags", "%s ");
                                for (j = 0; link_flags[i] && j < 32; j++) {
-                                       if (!(link_flags[i] & (1 << j)))
+                                       if (!(link_flags[i] & (1U << j)))
                                                continue;
-                                       NET_DUMP_UINT_ONLY(1 << j);
+                                       NET_DUMP_UINT_ONLY(1U << j);
                                }
                                NET_END_ARRAY("");
                        }