clone_private_mnt(): make sure that caller has CAP_SYS_ADMIN in the right userns
commit c28f922c9dcee0e4876a2c095939d77fe7e15116 upstream.
What we want is to verify there is that clone won't expose something
hidden by a mount we wouldn't be able to undo. "Wouldn't be able to undo"
may be a result of MNT_LOCKED on a child, but it may also come from
lacking admin rights in the userns of the namespace mount belongs to.
clone_private_mnt() checks the former, but not the latter.
There's a number of rather confusing CAP_SYS_ADMIN checks in various
userns during the mount, especially with the new mount API; they serve
different purposes and in case of clone_private_mnt() they usually,
but not always end up covering the missing check mentioned above.
BUG=b/437947543
TEST=presubmit
RELEASE_NOTE=Fixed CVE-2025-38499 in the linux kernel.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Reported-by: "Orlando, Noah" <Noah.Orlando@deshaw.com>
Fixes: 427215d85e8d ("ovl: prevent private clone if bind mount is not allowed")
Change-Id: I0d7662fe20249685a205090cab65f987a282f0af
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
[ merge conflict resolution: clone_private_mount() was reworked in
db04662e2f4f ("fs: allow detached mounts in clone_private_mount()").
Tweak the relevant ns_capable check so that it works on older kernels ]
Signed-off-by: Noah Orlando <Noah.Orlando@deshaw.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: chenglongtang <chenglongtang@google.com>
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/108828
Reviewed-by: Kevin Berry <kpberry@google.com>
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
1 file changed
