While user namespaces do not make the kernel more vulnerable, they are however
used to initiate exploits. Some users do not want to block namespace creation
for the entirety of the system, which some distributions provide. Instead, we
needed a way to have some applications be blocked, and others allowed. This is
not possible with those tools. Managing hierarchies also did not fit our case
because we're determining which tasks are allowed based on their attributes.
While exploring a solution, we first leveraged the LSM cred_prepare hook
because that is the closest hook to prevent a call to create_user_ns().
The calls look something like this:
cred = prepare_creds()
security_prepare_creds()
call_int_hook(cred_prepare, ...
if (cred)
create_user_ns(cred)
We noticed that error codes were not propagated from this hook and
introduced a patch [1] to propagate those errors.
The discussion notes that security_prepare_creds() is not appropriate for
MAC policies, and instead the hook is meant for LSM authors to prepare
credentials for mutation. [2]
Additionally, cred_prepare hook is not without problems. Handling the clone3
case is a bit more tricky due to the user space pointer passed to it. This
makes checking the syscall subject to a possible TOCTTOU attack.
Ultimately, we concluded that a better course of action is to introduce
a new security hook for LSM authors. [3]
This patch set first introduces a new security_create_user_ns() function
and userns_create LSM hook, then marks the hook as sleepable in BPF. The
following patches after include a BPF test and a patch for an SELinux
implementation.
We want to encourage use of user namespaces, and also cater the needs
of users/administrators to observe and/or control access. There is no
expectation of an impact on user space applications because access control
is opt-in, and users wishing to observe within a LSM context
Links:
1. https://lore.kernel.org/all/20220608150942.776446-1-fred@cloudflare.com/
2. https://lore.kernel.org/all/87y1xzyhub.fsf@email.froward.int.ebiederm.org/
3. https://lore.kernel.org/all/9fe9cd9f-1ded-a179-8ded-5fde8960a586@cloudflare…
Past discussions:
V4: https://lore.kernel.org/all/20220801180146.1157914-1-fred@cloudflare.com/
V3: https://lore.kernel.org/all/20220721172808.585539-1-fred@cloudflare.com/
V2: https://lore.kernel.org/all/20220707223228.1940249-1-fred@cloudflare.com/
V1: https://lore.kernel.org/all/20220621233939.993579-1-fred@cloudflare.com/
Changes since v4:
- Update commit description
- Update cover letter
Changes since v3:
- Explicitly set CAP_SYS_ADMIN to test namespace is created given
permission
- Simplify BPF test to use sleepable hook only
- Prefer unshare() over clone() for tests
Changes since v2:
- Rename create_user_ns hook to userns_create
- Use user_namespace as an object opposed to a generic namespace object
- s/domB_t/domA_t in commit message
Changes since v1:
- Add selftests/bpf: Add tests verifying bpf lsm create_user_ns hook patch
- Add selinux: Implement create_user_ns hook patch
- Change function signature of security_create_user_ns() to only take
struct cred
- Move security_create_user_ns() call after id mapping check in
create_user_ns()
- Update documentation to reflect changes
Frederick Lawler (4):
security, lsm: Introduce security_create_user_ns()
bpf-lsm: Make bpf_lsm_userns_create() sleepable
selftests/bpf: Add tests verifying bpf lsm userns_create hook
selinux: Implement userns_create hook
include/linux/lsm_hook_defs.h | 1 +
include/linux/lsm_hooks.h | 4 +
include/linux/security.h | 6 ++
kernel/bpf/bpf_lsm.c | 1 +
kernel/user_namespace.c | 5 +
security/security.c | 5 +
security/selinux/hooks.c | 9 ++
security/selinux/include/classmap.h | 2 +
.../selftests/bpf/prog_tests/deny_namespace.c | 102 ++++++++++++++++++
.../selftests/bpf/progs/test_deny_namespace.c | 33 ++++++
10 files changed, 168 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/deny_namespace.c
create mode 100644 tools/testing/selftests/bpf/progs/test_deny_namespace.c
--
2.30.2
The put lowers the reference count to 0 and frees ctx, reading it
afterwards is invalid. Move the put after the uses and determine the
last use by the reference count being 1.
Fixes: 39e940d4abfa ("selftests/xsk: Destroy BPF resources only when ctx refcount drops to 0")
Signed-off-by: Ian Rogers <irogers(a)google.com>
---
tools/testing/selftests/bpf/xsk.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/tools/testing/selftests/bpf/xsk.c b/tools/testing/selftests/bpf/xsk.c
index f2721a4ae7c5..0b3ff49c740d 100644
--- a/tools/testing/selftests/bpf/xsk.c
+++ b/tools/testing/selftests/bpf/xsk.c
@@ -1237,15 +1237,15 @@ void xsk_socket__delete(struct xsk_socket *xsk)
ctx = xsk->ctx;
umem = ctx->umem;
- xsk_put_ctx(ctx, true);
-
- if (!ctx->refcount) {
+ if (ctx->refcount == 1) {
xsk_delete_bpf_maps(xsk);
close(ctx->prog_fd);
if (ctx->has_bpf_link)
close(ctx->link_fd);
}
+ xsk_put_ctx(ctx, true);
+
err = xsk_get_mmap_offsets(xsk->fd, &off);
if (!err) {
if (xsk->rx) {
--
2.37.2.789.g6183377224-goog
Hi,
here comes the v9 of the HID-BPF series.
Again, for a full explanation of HID-BPF, please refer to the last patch
in this series (23/23).
This version sees some minor improvements compared to v7 and v8, only
focusing on the reviews I got. (v8 was a single patch update)
- patch 1/24 in v7 was dropped as it is already fixed upstream
- patch 1/23 in v9 is now capable of handling all functions, not just
kfuncs (tested with the selftests only)
- some minor nits from Greg's review
- a rebase on top of the current bpf-next tree as the kfunc definition
changed (for the better).
Cheers,
Benjamin
Benjamin Tissoires (23):
bpf/verifier: allow all functions to read user provided context
bpf/verifier: do not clear meta in check_mem_size
selftests/bpf: add test for accessing ctx from syscall program type
bpf/verifier: allow kfunc to return an allocated mem
selftests/bpf: Add tests for kfunc returning a memory pointer
bpf: prepare for more bpf syscall to be used from kernel and user
space.
libbpf: add map_get_fd_by_id and map_delete_elem in light skeleton
HID: core: store the unique system identifier in hid_device
HID: export hid_report_type to uapi
HID: convert defines of HID class requests into a proper enum
HID: Kconfig: split HID support and hid-core compilation
HID: initial BPF implementation
selftests/bpf: add tests for the HID-bpf initial implementation
HID: bpf: allocate data memory for device_event BPF programs
selftests/bpf/hid: add test to change the report size
HID: bpf: introduce hid_hw_request()
selftests/bpf: add tests for bpf_hid_hw_request
HID: bpf: allow to change the report descriptor
selftests/bpf: add report descriptor fixup tests
selftests/bpf: Add a test for BPF_F_INSERT_HEAD
samples/bpf: HID: add new hid_mouse example
samples/bpf: HID: add Surface Dial example
Documentation: add HID-BPF docs
Documentation/hid/hid-bpf.rst | 512 +++++++++
Documentation/hid/index.rst | 1 +
drivers/Makefile | 2 +-
drivers/hid/Kconfig | 20 +-
drivers/hid/Makefile | 2 +
drivers/hid/bpf/Kconfig | 17 +
drivers/hid/bpf/Makefile | 11 +
drivers/hid/bpf/entrypoints/Makefile | 93 ++
drivers/hid/bpf/entrypoints/README | 4 +
drivers/hid/bpf/entrypoints/entrypoints.bpf.c | 66 ++
.../hid/bpf/entrypoints/entrypoints.lskel.h | 682 ++++++++++++
drivers/hid/bpf/hid_bpf_dispatch.c | 526 ++++++++++
drivers/hid/bpf/hid_bpf_dispatch.h | 28 +
drivers/hid/bpf/hid_bpf_jmp_table.c | 577 ++++++++++
drivers/hid/hid-core.c | 49 +-
include/linux/bpf.h | 9 +-
include/linux/btf.h | 10 +
include/linux/hid.h | 38 +-
include/linux/hid_bpf.h | 148 +++
include/uapi/linux/hid.h | 26 +-
include/uapi/linux/hid_bpf.h | 25 +
kernel/bpf/btf.c | 109 +-
kernel/bpf/syscall.c | 10 +-
kernel/bpf/verifier.c | 64 +-
net/bpf/test_run.c | 21 +
samples/bpf/.gitignore | 2 +
samples/bpf/Makefile | 27 +
samples/bpf/hid_mouse.bpf.c | 134 +++
samples/bpf/hid_mouse.c | 161 +++
samples/bpf/hid_surface_dial.bpf.c | 161 +++
samples/bpf/hid_surface_dial.c | 232 ++++
tools/include/uapi/linux/hid.h | 62 ++
tools/include/uapi/linux/hid_bpf.h | 25 +
tools/lib/bpf/skel_internal.h | 23 +
tools/testing/selftests/bpf/Makefile | 5 +-
tools/testing/selftests/bpf/config | 3 +
tools/testing/selftests/bpf/prog_tests/hid.c | 990 ++++++++++++++++++
.../selftests/bpf/prog_tests/kfunc_call.c | 76 ++
tools/testing/selftests/bpf/progs/hid.c | 206 ++++
.../selftests/bpf/progs/kfunc_call_test.c | 125 +++
40 files changed, 5198 insertions(+), 84 deletions(-)
create mode 100644 Documentation/hid/hid-bpf.rst
create mode 100644 drivers/hid/bpf/Kconfig
create mode 100644 drivers/hid/bpf/Makefile
create mode 100644 drivers/hid/bpf/entrypoints/Makefile
create mode 100644 drivers/hid/bpf/entrypoints/README
create mode 100644 drivers/hid/bpf/entrypoints/entrypoints.bpf.c
create mode 100644 drivers/hid/bpf/entrypoints/entrypoints.lskel.h
create mode 100644 drivers/hid/bpf/hid_bpf_dispatch.c
create mode 100644 drivers/hid/bpf/hid_bpf_dispatch.h
create mode 100644 drivers/hid/bpf/hid_bpf_jmp_table.c
create mode 100644 include/linux/hid_bpf.h
create mode 100644 include/uapi/linux/hid_bpf.h
create mode 100644 samples/bpf/hid_mouse.bpf.c
create mode 100644 samples/bpf/hid_mouse.c
create mode 100644 samples/bpf/hid_surface_dial.bpf.c
create mode 100644 samples/bpf/hid_surface_dial.c
create mode 100644 tools/include/uapi/linux/hid.h
create mode 100644 tools/include/uapi/linux/hid_bpf.h
create mode 100644 tools/testing/selftests/bpf/prog_tests/hid.c
create mode 100644 tools/testing/selftests/bpf/progs/hid.c
--
2.36.1