Re: [PATCH 12/13] selftests/ftrace: add uprobe tests on overlayfs

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential
issues to consider:
- [Low] selftests/ftrace: cleanup() in uprobe overlayfs test fails if
  event is enabled
- [Low] selftests/ftrace: uprobe overlayfs test misses tmpfs xattr skip
  and configs
--

commit cdef3f0121f6552797f32e8a89d02391a6081a77
Author: Christian Brauner <brauner@kernel.org>

selftests/ftrace: add uprobe tests on overlayfs

This commit adds an ftrace selftest that exercises creating and firing uprobe
events on overlayfs metacopy files backed by a data-only layer.

> diff --git a/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_uprobe_overlayfs.tc b/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_uprobe_overlayfs.tc
> new file mode 100644
> index 0000000000000..a4351e6a3b181
> --- /dev/null
> +++ b/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_uprobe_overlayfs.tc
> @@ -0,0 +1,92 @@
[ ... ]
> +cleanup() {
> +  echo > uprobe_events
> +  umount $OVL/merged 2> /dev/null || :
> +  umount $OVL 2> /dev/null || :
> +}
> +trap cleanup EXIT

[Severity: Low]
Does cleanup() fail to remove myevent and unmount the filesystems if the test
exits while myevent is enabled?

ftracetest runs test scripts under set -e.  If executing $OVL/merged/sh fails
between enabling and disabling events/uprobes/myevent/enable, the EXIT trap
runs while myevent is still enabled.  Truncating uprobe_events then returns
-EBUSY from trace_uprobe_is_busy() and aborts cleanup() under set -e before
the umount commands run, leaving the uprobe registered and the overlayfs and
tmpfs mounts leaked.  Writing 0 to events/enable at the start of cleanup()
would avoid this.

> +
> +mkdir $OVL/lower $OVL/data $OVL/merged
> +
> +# A metacopy file whose data lives in the data-only layer.
> +REALBIN=`readlink -f /bin/sh`
> +cp $REALBIN $OVL/data/sh
> +truncate -s `stat -c %s $REALBIN` $OVL/lower/sh
> +chmod 755 $OVL/lower/sh
> +setfattr -n trusted.overlay.metacopy $OVL/lower/sh
> +setfattr -n trusted.overlay.redirect -v /sh $OVL/lower/sh

[Severity: Low]
Will this test fail instead of skipping with exit_unsupported when
CONFIG_TMPFS_XATTR is disabled?

tmpfs only supports trusted.* xattrs when CONFIG_TMPFS_XATTR is enabled, which
defaults to n and is not selected by CONFIG_OVERLAY_FS.  Without it, setfattr
on $OVL/lower/sh fails with EOPNOTSUPP and aborts the script under set -e.
Also, should CONFIG_OVERLAY_FS=y and CONFIG_TMPFS_XATTR=y be added to
tools/testing/selftests/ftrace/config?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261115-work-ovl-d_real-v1-0-ca155efbcb2e@kernel.org?part=12