On Wed, Nov 29, 2023 at 11:22:03AM +0100, Miklos Szeredi wrote:

On Wed, 29 Nov 2023 at 10:53, Christian Brauner [off-list ref] wrote:

quoted

On Tue, 28 Nov 2023 17:03:31 +0100, Miklos Szeredi wrote:

quoted

This came out from me thinking about the best libc API.  It contains a few
changes that simplify and (I think) improve the interface.

Tree:

  git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git#vfs.mount

[...]

Afaict, all changes as discussed. Thanks. I folded the fixes into the
main commit. Links to the patches that were folded are in the commit
message and explained in there as well. The final commit is now rather
small and easy to read.

Looks good, thanks for folding the patches.

quoted

   * Remove explicit LISTMOUNT_UNREACHABLE flag (cf. [1]). That
     functionality can simply be made available by checking for required
     privileges. If the caller is sufficiently privileged then list mounts
     that can't be reached from the current root. If the caller isn't skip
     mounts that can't be reached from the current root. This also makes
     permission checking consistent with statmount() (cf. [3]).

Skipping mounts based on privileges was what the initial version did.
That inconsistency was the reason for introducing
LISTMOUNT_UNREACHABLE.  The final version doesn't skip mounts based on
privileges, either all submounts are listed or the request is rejected
with -EPERM.

Yeah, I phrased that badly. What I meant to convey is that mounts not
reachable from the current root are not reported as in skipped in the
loop. I've simplified this down to:

* Remove explicit LISTMOUNT_UNREACHABLE flag (cf. [1]) and fail if mount
  is unreachable from current root. This also makes permission checking
  consistent with statmount() (cf. [3]).