linux.git/kernel/nscommon.c, branch v6.18.21

nsfs: tighten permission checks for ns iteration ioctls

2026-03-25T10:10:33+00:00

[ Upstream commit e6b899f08066e744f89df16ceb782e06868bd148 ]

Even privileged services should not necessarily be able to see other
privileged service's namespaces so they can't leak information to each
other. Use may_see_all_namespaces() helper that centralizes this policy
until the nstree adapts.

Link: https://patch.msgid.link/20260226-work-visibility-fixes-v1-1-d2c2853313bd@kernel.org
Fixes: a1d220d9dafa ("nsfs: iterate through mount namespaces")
Reviewed-by: Jeff Layton 
Cc: stable@kernel.org # v6.12+
Signed-off-by: Christian Brauner 
[ context ]
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

ns: drop assert

2025-09-25T07:23:54+00:00

Otherwise we warn when e.g., no namespaces are configured but the
initial namespace for is still around.

Reviewed-by: Jan Kara 
Signed-off-by: Christian Brauner

ns: move ns type into struct ns_common

2025-09-25T07:23:54+00:00

It's misplaced in struct proc_ns_operations and ns->ops might be NULL if
the namespace is compiled out but we still want to know the type of the
namespace for the initial namespace struct.

Reviewed-by: Jan Kara 
Signed-off-by: Christian Brauner

ns: add ns_debug()

2025-09-22T12:47:10+00:00

Add ns_debug() that asserts that the correct operations are used for the
namespace type.

Reviewed-by: Jan Kara 
Signed-off-by: Christian Brauner

ns: rename to __ns_ref

2025-09-19T14:22:38+00:00

Make it easier to grep and rename to ns_count.

Reviewed-by: Jan Kara 
Signed-off-by: Christian Brauner

ns: add ns_common_free()

2025-09-19T14:22:36+00:00

And drop ns_free_inum(). Anything common that can be wasted centrally
should be wasted in the new common helper.

Reviewed-by: Jan Kara 
Signed-off-by: Christian Brauner

nscommon: simplify initialization

2025-09-19T12:26:19+00:00

There's a lot of information that namespace implementers don't need to
know about at all. Encapsulate this all in the initialization helper.

Reviewed-by: Jan Kara 
Signed-off-by: Christian Brauner

mnt: simplify ns_common_init() handling

2025-09-19T12:26:18+00:00

Assign the reserved MNT_NS_ANON_INO sentinel to anonymous mount
namespaces and cleanup the initial mount ns allocation. This is just a
preparatory patch and the ns->inum check in ns_common_init() will be
dropped in the next patch.

Reviewed-by: Jan Kara 
Signed-off-by: Christian Brauner

nscommon: move to separate file

2025-09-19T12:26:18+00:00

It's really awkward spilling the ns common infrastructure into multiple
headers. Move it to a separate file.

Reviewed-by: Jan Kara 
Signed-off-by: Christian Brauner