Messages in this thread | | | From | Frederick Lawler <> | Subject | [PATCH 0/2] Introduce security_create_user_ns() | Date | Tue, 21 Jun 2022 18:39:37 -0500 |
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While creating a LSM BPF MAC policy to block user namespace creation, we used 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]
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 create_user_ns LSM hook, then marks the hook as sleepable in BPF.
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.com/
Frederick Lawler (2): security, lsm: Introduce security_create_user_ns() bpf-lsm: Make bpf_lsm_create_user_ns() sleepable
include/linux/lsm_hook_defs.h | 2 ++ include/linux/lsm_hooks.h | 5 +++++ include/linux/security.h | 8 ++++++++ kernel/bpf/bpf_lsm.c | 1 + kernel/user_namespace.c | 5 +++++ security/security.c | 6 ++++++ 6 files changed, 27 insertions(+)
-- 2.30.2
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