Re: [LTP] syscalls/fanotify26: Add test for nested permission events

[linuxtestproject.agent@gmail.com]

Hi Edvard,

On Tue, Oct 27, 2026 at 08:37:01PM +0100, Edvard Conrad wrote:
> syscalls/fanotify26: Add test for nested permission events

> --- /dev/null
> +++ b/testcases/kernel/syscalls/fanotify/fanotify26.c
> @@ -0,0 +1,185 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*\
> + * Check that a permission event on a stacked filesystem does not deadlock the

A copyright header block ("/* Copyright (c) 2026 Edvard Conrad
<edvard@tuta.io> */") is missing after the SPDX license identifier.

> +	if (tc->mark_backing && filesystem_mark_unsupported) {
> +		tst_res(TCONF, "FAN_MARK_FILESYSTEM not supported");
> +		return;
> +	}
> +
> +	fd_notify = SAFE_FANOTIFY_INIT(FAN_CLASS_CONTENT, O_RDONLY);
> +
> +	SAFE_FANOTIFY_MARK(fd_notify, FAN_MARK_ADD | FAN_MARK_FILESYSTEM,
> +			   FAN_OPEN_PERM, AT_FDCWD, OVL_MNT);

Both test cases use FAN_MARK_FILESYSTEM on OVL_MNT, so gating
filesystem_mark_unsupported on tc->mark_backing causes the first test case to
fail with TBROK when FAN_MARK_FILESYSTEM is unsupported on overlayfs or in
the kernel. Use REQUIRE_MARK_TYPE_SUPPORTED_ON_FS(FAN_MARK_FILESYSTEM,
OVL_MNT) and REQUIRE_MARK_TYPE_SUPPORTED_ON_FS(FAN_MARK_FILESYSTEM,
BACKING_MNT) in setup() and drop filesystem_mark_unsupported.

> +		fd = open(OVL_FILE, O_RDONLY);
> +		if (fd >= 0)
> +			SAFE_CLOSE(fd);
> +		exit(0);
> +	}
> +
> +	/* The opener sleeps in the kernel once its event is queued. */
> +	if (TST_PROCESS_STATE_WAIT(opener, 'D', WAIT_MSEC)) {
> +		SAFE_CLOSE(fd_notify);
> +		tst_brk(TBROK, "Open generated no permission event");
> +	}

Use "if (fd != -1)" to check file descriptor validity in opener. Also,
SAFE_CLOSE(fd_notify) before tst_brk() is redundant because cleanup() already
closes fd_notify.

> +	reader = SAFE_FORK();
> +	if (!reader) {
> +		answer_one_event();
> +		exit(0);
> +	}
> +
> +	if (TST_PROCESS_STATE_WAIT(reader, 'Z', WAIT_MSEC)) {
> +		tst_res(TFAIL,
> +			"Listener blocked in read() by a nested event");
> +		SAFE_KILL(reader, SIGKILL);
> +	} else {
> +		tst_res(TPASS, "Listener answered the event");
> +	}
> +
> +	SAFE_WAITPID(reader, NULL, 0);

Inferring TPASS from the child reaching 'Z' state and reaping it with
SAFE_WAITPID(reader, NULL, 0) hides abnormal child termination. Call
tst_res(TPASS, "Listener answered the event") at the end of
answer_one_event() in the child, and only call SAFE_WAITPID(reader, NULL, 0)
after SAFE_KILL(reader, SIGKILL), letting the library reap the children on
the normal path.

> +	/* Releases whatever is still queued, so the opener can finish. */
> +	SAFE_CLOSE(fd_notify);
> +	fd_notify = -1;

Setting fd_notify = -1 is redundant because SAFE_CLOSE() already resets its
argument to -1.

> +static void cleanup(void)
> +{
> +	if (fd_notify >= 0)
> +		SAFE_CLOSE(fd_notify);
> +}

Use "if (fd_notify != -1)" instead of "if (fd_notify >= 0)".

Verdict - Needs revision

---
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LTP AI Reviewer

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