Re: [PATCH 03/17] selftests/filesystems: check that a busy submount survives a synchronous umount

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] selftests: temporary directory leak on early SKIP in test setup
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commit 02ea3b012fe359abd8677445122fce027a20c695
Author: Christian Brauner <brauner@kernel.org>

selftests/filesystems: check that a busy submount survives a synchronous umount

This commit adds a test for the shrinkable submounts of a synchronous
umount. It verifies that a busy submount will survive a synchronous umount
operation and result in an EBUSY error.

> diff --git a/tools/testing/selftests/filesystems/umount_propagation/shrink_submounts_test.c b/tools/testing/selftests/filesystems/umount_propagation/shrink_submounts_test.c
> new file mode 100644
> index 0000000000000..43efb7faf95ce
> --- /dev/null
> +++ b/tools/testing/selftests/filesystems/umount_propagation/shrink_submounts_test.c
> @@ -0,0 +1,205 @@
[ ... ]
> +FIXTURE_SETUP(shrink_submounts)
> +{
> +	struct stat st;
> +	char p[PATH_LEN];
> +
> +	self->mounted = false;
> +	self->fan = -1;
> +
> +	if (geteuid() != 0)
> +		SKIP(return, "test requires CAP_SYS_ADMIN");
> +
> +	ASSERT_EQ(unshare(CLONE_NEWNS), 0);
> +	ASSERT_EQ(mount("", "/", NULL, MS_REC | MS_PRIVATE, NULL), 0);
> +
> +	snprintf(self->base, sizeof(self->base), "/tmp/shrink_submounts.XXXXXX");
> +	ASSERT_NE(mkdtemp(self->base), NULL);
> +	ASSERT_EQ(mount("tmpfs", self->base, "tmpfs", 0, NULL), 0);
> +	self->mounted = true;
> +	ASSERT_EQ(mount(NULL, self->base, NULL, MS_PRIVATE, NULL), 0);
> +
> +	snprintf(p, sizeof(p), "%s/dbg", self->base);
> +	ASSERT_EQ(mkdir(p, 0755), 0);
> +	if (mount("debugfs", p, "debugfs", 0, NULL))
> +		SKIP(return, "test requires debugfs");

[Severity: Low]
Does this code leak the newly created temporary directory on the host?

If the test skips here due to missing debugfs, the kselftest harness
terminates the setup early and skips FIXTURE_TEARDOWN(). While memory and
file descriptor leaks in tests are typically cleaned up by the OS on exit,
this mkdtemp directory in /tmp persists on the host filesystem across
test runs.

> +	snprintf(self->automount, sizeof(self->automount), "%s/dbg/tracing",
> +		 self->base);
> +	snprintf(p, sizeof(p), "%s/dbg/tracing/.", self->base);
> +	if (stat(p, &st))
> +		SKIP(return, "test requires the tracefs automount");

[Severity: Low]
Similarly, does exiting here via SKIP() leave the mkdtemp directory
abandoned without cleanup on the host?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260930-work-mount-fixes-3-v1-0-be34c83956ae@kernel.org?part=3