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    Subject[PATCH 4.19 050/219] selftests/bpf: Correct path to include msg + path
    Date
    From: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>

    [ 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 ‘setup_cgroup_environment’:
    samples/bpf/../../tools/testing/selftests/bpf/cgroup_helpers.c:52:34:
    warning: ‘/cgroup.controllers’ 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: ‘snprintf’ 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: ‘/cgroup.subtree_control’ 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: ‘snprintf’ 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@linaro.org>
    Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
    Acked-by: Song Liu <songliubraving@fb.com>
    Link: https://lore.kernel.org/bpf/20191002120404.26962-3-ivan.khoronzhuk@linaro.org
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    tools/testing/selftests/bpf/cgroup_helpers.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/tools/testing/selftests/bpf/cgroup_helpers.c b/tools/testing/selftests/bpf/cgroup_helpers.c
    index cf16948aad4a..6af24f9a780d 100644
    --- a/tools/testing/selftests/bpf/cgroup_helpers.c
    +++ b/tools/testing/selftests/bpf/cgroup_helpers.c
    @@ -44,7 +44,7 @@
    */
    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


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