[PATCH AUTOSEL 4.14 022/130] selftests/bpf: Correct path to include msg + path

[Sasha Levin]

From: Ivan Khoronzhuk <ivan.khoronzhuk@xxxxxxxxxx>

[ Upstream commit c588146378962786ddeec817f7736a53298a7b01 ]

The "path" buf is supposed to contain path + printf msg up to 24 bytes.
It will be cut anyway, but compiler generates truncation warns like:

"
samples/bpf/../../tools/testing/selftests/bpf/cgroup_helpers.c: In
function âsetup_cgroup_environmentâ:
samples/bpf/../../tools/testing/selftests/bpf/cgroup_helpers.c:52:34:
warning: â/cgroup.controllersâ directive output may be truncated
writing 19 bytes into a region of size between 1 and 4097
[-Wformat-truncation=]
snprintf(path, sizeof(path), "%s/cgroup.controllers", cgroup_path);
				  ^~~~~~~~~~~~~~~~~~~
samples/bpf/../../tools/testing/selftests/bpf/cgroup_helpers.c:52:2:
note: âsnprintfâ output between 20 and 4116 bytes into a destination
of size 4097
snprintf(path, sizeof(path), "%s/cgroup.controllers", cgroup_path);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
samples/bpf/../../tools/testing/selftests/bpf/cgroup_helpers.c:72:34:
warning: â/cgroup.subtree_controlâ directive output may be truncated
writing 23 bytes into a region of size between 1 and 4097
[-Wformat-truncation=]
snprintf(path, sizeof(path), "%s/cgroup.subtree_control",
				  ^~~~~~~~~~~~~~~~~~~~~~~
cgroup_path);
samples/bpf/../../tools/testing/selftests/bpf/cgroup_helpers.c:72:2:
note: âsnprintfâ output between 24 and 4120 bytes into a destination
of size 4097
snprintf(path, sizeof(path), "%s/cgroup.subtree_control",
cgroup_path);
"

In order to avoid warns, lets decrease buf size for cgroup workdir on
24 bytes with assumption to include also "/cgroup.subtree_control" to
the address. The cut will never happen anyway.

Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@xxxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Acked-by: Song Liu <songliubraving@xxxxxx>
Link: https://lore.kernel.org/bpf/20191002120404.26962-3-ivan.khoronzhuk@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 samples/bpf/cgroup_helpers.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/samples/bpf/cgroup_helpers.c b/samples/bpf/cgroup_helpers.c
index 09afaddfc9ba9..b5c09cd6c7bd7 100644
--- a/samples/bpf/cgroup_helpers.c
+++ b/samples/bpf/cgroup_helpers.c
@@ -43,7 +43,7 @@
  */
 int setup_cgroup_environment(void)
 {
-	char cgroup_workdir[PATH_MAX + 1];
+	char cgroup_workdir[PATH_MAX - 24];
 
 	format_cgroup_path(cgroup_workdir, "");
 
-- 
2.20.1