Re: [PATCH v6 1/1] selftests/landlock: skip overlayfs test when kernel not support it

[Jeff Xu <jeffxu@google.com>]

On Thu, Dec 29, 2022 at 12:18 PM Guenter Roeck <groeck@google.com> wrote:
>
> On Thu, Dec 29, 2022 at 12:12 PM <jeffxu@chromium.org> wrote:
> >
> > From: Jeff Xu <jeffxu@google.com>
> >
> > Overlayfs can be disabled in kernel config, causing related tests to
> > fail. Add check for overlayfs’s supportability at runtime,
> > so we can call SKIP() when needed.
> >
> > Signed-off-by: Jeff Xu <jeffxu@google.com>
> > ---
> >  tools/testing/selftests/landlock/fs_test.c | 56 ++++++++++++++++++++++
> >  1 file changed, 56 insertions(+)
> >
> > diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
> > index 21a2ce8fa739..2d84c055f86f 100644
> > --- a/tools/testing/selftests/landlock/fs_test.c
> > +++ b/tools/testing/selftests/landlock/fs_test.c
> > @@ -11,6 +11,7 @@
> >  #include <fcntl.h>
> >  #include <linux/landlock.h>
> >  #include <sched.h>
> > +#include <stdio.h>
> >  #include <string.h>
> >  #include <sys/capability.h>
> >  #include <sys/mount.h>
> > @@ -62,6 +63,7 @@ static const char dir_s3d1[] = TMP_DIR "/s3d1";
> >  static const char dir_s3d2[] = TMP_DIR "/s3d1/s3d2";
> >  static const char dir_s3d3[] = TMP_DIR "/s3d1/s3d2/s3d3";
> >
> > +static const char proc_filesystems[] = "/proc/filesystems";
> >  /*
> >   * layout1 hierarchy:
> >   *
> > @@ -169,6 +171,48 @@ static int remove_path(const char *const path)
> >         return err;
> >  }
> >
> > +static bool fgrep(FILE *inf, const char *str)
> > +{
> > +       char line[32];
> > +       int slen = strlen(str);
> > +
> > +       while (!feof(inf)) {
> > +               if (!fgets(line, sizeof(line), inf))
> > +                       break;
> > +               if (strncmp(line, str, slen))
> > +                       continue;
> > +
> > +               return true;
> > +       }
> > +
> > +       return false;
> > +}
> > +
> > +static bool supports_overlayfs(void)
> > +{
> > +       char *res;
> > +       bool ret = false;
>
> Unnecessary initialization.
>
> > +       FILE *inf = fopen(proc_filesystems, "r");
> > +
> > +       /*
> > +        * If fopen failed, return supported.
> > +        * This help detect missing file (shall not
> > +        * happen).
> > +        */
> > +       if (!inf)
> > +               return true;
> > +
> > +       ret = fgrep(inf, "nodev\toverlay\n");
> > +
> > +       if (res)
> > +               free(res);
>
> Either I am missing something, or res is neither initialized nor used.
>
Hoops, this is a bug, and I'm missing a test with a kernel with
overlayfs enabled.
I will send V7.

> Guenter
>
> > +
> > +       fclose(inf);
> > +
> > +       return ret;
> > +}
> > +
> > +
> >  static void prepare_layout(struct __test_metadata *const _metadata)
> >  {
> >         disable_caps(_metadata);
> > @@ -3404,6 +3448,9 @@ FIXTURE(layout2_overlay) {};
> >
> >  FIXTURE_SETUP(layout2_overlay)
> >  {
> > +       if (!supports_overlayfs())
> > +               SKIP(return, "overlayfs is not supported");
> > +
> >         prepare_layout(_metadata);
> >
> >         create_directory(_metadata, LOWER_BASE);
> > @@ -3440,6 +3487,9 @@ FIXTURE_SETUP(layout2_overlay)
> >
> >  FIXTURE_TEARDOWN(layout2_overlay)
> >  {
> > +       if (!supports_overlayfs())
> > +               SKIP(return, "overlayfs is not supported");
> > +
> >         EXPECT_EQ(0, remove_path(lower_do1_fl3));
> >         EXPECT_EQ(0, remove_path(lower_dl1_fl2));
> >         EXPECT_EQ(0, remove_path(lower_fl1));
> > @@ -3471,6 +3521,9 @@ FIXTURE_TEARDOWN(layout2_overlay)
> >
> >  TEST_F_FORK(layout2_overlay, no_restriction)
> >  {
> > +       if (!supports_overlayfs())
> > +               SKIP(return, "overlayfs is not supported");
> > +
> >         ASSERT_EQ(0, test_open(lower_fl1, O_RDONLY));
> >         ASSERT_EQ(0, test_open(lower_dl1, O_RDONLY));
> >         ASSERT_EQ(0, test_open(lower_dl1_fl2, O_RDONLY));
> > @@ -3634,6 +3687,9 @@ TEST_F_FORK(layout2_overlay, same_content_different_file)
> >         size_t i;
> >         const char *path_entry;
> >
> > +       if (!supports_overlayfs())
> > +               SKIP(return, "overlayfs is not supported");
> > +
> >         /* Sets rules on base directories (i.e. outside overlay scope). */
> >         ruleset_fd = create_ruleset(_metadata, ACCESS_RW, layer1_base);
> >         ASSERT_LE(0, ruleset_fd);
> > --
> > 2.39.0.314.g84b9a713c41-goog
> >