Re: [PATCH 1/5] fanotify20: Allow FAN_REPORT_PIDFD with FAN_REPORT_TID on v7.2+

On Tue, Jun 16, 2026 at 9:40 AM Jan Kara <[email protected]> wrote:
>
> On Tue 16-06-26 02:06:25, AnonymeMeow wrote:
> > fanotify_init() used to reject FAN_REPORT_PIDFD combined with
> > FAN_REPORT_TID with EINVAL. Since Linux v7.2, fanotify supports
> > reporting pidfds for thread IDs, so this combination is expected to
> > succeed.
> >
> > Keep expecting EINVAL on older kernels and adjust the test expectation
> > based on the running kernel version.
> >
> > Signed-off-by: AnonymeMeow <[email protected]>
>
> Thanks for the fixes! Some comment below. And take your time with final
> exams, that's more important than some failing LTP tests :)
>
> > diff --git a/testcases/kernel/syscalls/fanotify/fanotify20.c b/testcases/kernel/syscalls/fanotify/fanotify20.c
> > index b32ecf6aa..9a78f6ff0 100644
> > --- a/testcases/kernel/syscalls/fanotify/fanotify20.c
> > +++ b/testcases/kernel/syscalls/fanotify/fanotify20.c
> > @@ -8,13 +8,14 @@
> >
> >  /*\
> >   * This source file contains a test case which ensures that the
> > - * :manpage:`fanotify(7)` API returns an expected error code when provided an
> > - * invalid initialization flag alongside FAN_REPORT_PIDFD. Additionally, it
> > - * checks that the operability with existing FAN_REPORT_* flags is maintained
> > - * and functioning as intended.
> > + * :manpage:`fanotify(7)` API returns an expected error code when provided
> > + * unsupported initialization flags, e.g. FAN_REPORT_PIDFD combined with
> > + * FAN_REPORT_TID. Additionally, it checks that the operability with
> > + * supported FAN_REPORT_* flags is maintained and functioning as intended.
> >   *
> >   * NOTE: FAN_REPORT_PIDFD support was added in v5.15-rc1 in
> >   * af579beb666a ("fanotify: add pidfd support to the fanotify API").
> > + * FAN_REPORT_PIDFD combined with FAN_REPORT_TID is supported since v7.2-rc1.

Can add the upstream commit here.

> >   */
> >
> >  #define _GNU_SOURCE
> > @@ -26,8 +27,10 @@
> >
> >  #define MOUNT_PATH   "fs_mnt"
> >  #define FLAGS_DESC(x) .flags = x, .desc = #x
> > +#define PIDFD_TID_FLAGS (FAN_REPORT_PIDFD | FAN_REPORT_TID)
> >
> >  static int fd;
> > +static int thread_pidfd_supported;
> >
> >  static struct test_case_t {
> >       unsigned int flags;
> > @@ -51,17 +54,21 @@ static void do_setup(void)
> >        */
> >       REQUIRE_FANOTIFY_INIT_FLAGS_SUPPORTED_ON_FS(FAN_REPORT_PIDFD,
> >                                                   MOUNT_PATH);
> > +
> > +     thread_pidfd_supported = tst_kvercmp(7, 2, 0) >= 0;
> >  }
> >
> >  static void do_test(unsigned int i)
> >  {
> >       struct test_case_t *tc = &test_cases[i];
> > +     int exp_errno = (tc->flags & PIDFD_TID_FLAGS) == PIDFD_TID_FLAGS &&
> > +                     thread_pidfd_supported ? 0 : tc->exp_errno;
> >
> > -     tst_res(TINFO, "Test %s on %s", tc->exp_errno ? "fail" : "pass",
> > +     tst_res(TINFO, "Test %s on %s", exp_errno ? "fail" : "pass",
> >               tc->desc);
> >
> >       TST_EXP_FD_OR_FAIL(fd = fanotify_init(tc->flags, O_RDONLY),
> > -                        tc->exp_errno);
> > +                        exp_errno);
>
> Hum, this looks somewhat ugly. Ideally we'd initialize test case .exp_errno
> accordingly to the expected return of the syscall (but that's not really
> possible because the initializer has to be constant). Checking how other
> tests handle it, I think we can clone the tests to two. One that expects
> failure and is skipped for kernels >= 7.2 and one that expects success and
> is skipped for kernels < 7.2. And we can have in the test description
> .min_kver and .max_kver fields that would store for which kernel versions
> the test should be performed.

LOL there is nothing to test in the >= 7.2 test.

The test that these flag combination are allowed:
                FLAGS_DESC(FAN_REPORT_PIDFD | FAN_REPORT_TID),
                FLAGS_DESC(FAN_REPORT_PIDFD | FAN_REPORT_FID |
FAN_REPORT_DFID_NAME),

Is already "tested" by the tests that use them.
and we don't have any tests that >= 5.10 has support for
FAN_MARK_FILESYSTEM etc.

Easiest is to just skip fanotify20 for version >= 7.2

Thanks,
Amir.

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