[bpf-next] bpf: add small subset of SECURITY_PATH hooks to BPF sleepable_lsm_hooks list

Commit Message

Matt Bobrowski Dec. 8, 2023, 3:32 p.m. UTC

security_path_* based LSM hooks appear to be generally missing from
the sleepable_lsm_hooks list. Initially add a small subset of them to
the preexisting sleepable_lsm_hooks list so that sleepable BPF helpers
like bpf_d_path() can be used from sleepable BPF LSM based programs.

The security_path_* hooks added in this patch are similar to the
security_inode_* counterparts that already exist in the
sleepable_lsm_hooks list, and are called in roughly similar points and
contexts. Presumably, making them OK to be also annotated as
sleepable.

Building a kernel with DEBUG_ATOMIC_SLEEP options enabled and running
reasonable workloads stimulating activity that would be intercepted by
such security hooks didn't show any splats.

Notably, I haven't added all the security_path_* LSM hooks that are
available as I don't need them at this point in time.

Signed-off-by: Matt Bobrowski <[e-mail]>
---
 kernel/bpf/bpf_lsm.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

Comments

KP Singh Dec. 12, 2023, 6:45 p.m. UTC | #1

On Fri, Dec 8, 2023 at 4:32 PM Matt Bobrowski <[e-mail]> wrote:
>
> security_path_* based LSM hooks appear to be generally missing from
> the sleepable_lsm_hooks list. Initially add a small subset of them to
> the preexisting sleepable_lsm_hooks list so that sleepable BPF helpers
> like bpf_d_path() can be used from sleepable BPF LSM based programs.
>
> The security_path_* hooks added in this patch are similar to the
> security_inode_* counterparts that already exist in the
> sleepable_lsm_hooks list, and are called in roughly similar points and
> contexts. Presumably, making them OK to be also annotated as
> sleepable.
>
> Building a kernel with DEBUG_ATOMIC_SLEEP options enabled and running
> reasonable workloads stimulating activity that would be intercepted by
> such security hooks didn't show any splats.
>
> Notably, I haven't added all the security_path_* LSM hooks that are
> available as I don't need them at this point in time.
>
> Signed-off-by: Matt Bobrowski <[e-mail]>

Acked-by: KP Singh <[e-mail]>

[e-mail] Dec. 14, 2023, 1 a.m. UTC | #2

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <[e-mail]>:

On Fri, 8 Dec 2023 15:32:48 +0000 you wrote:
> security_path_* based LSM hooks appear to be generally missing from
> the sleepable_lsm_hooks list. Initially add a small subset of them to
> the preexisting sleepable_lsm_hooks list so that sleepable BPF helpers
> like bpf_d_path() can be used from sleepable BPF LSM based programs.
> 
> The security_path_* hooks added in this patch are similar to the
> security_inode_* counterparts that already exist in the
> sleepable_lsm_hooks list, and are called in roughly similar points and
> contexts. Presumably, making them OK to be also annotated as
> sleepable.
> 
> [...]

Here is the summary with links:
  - [bpf-next] bpf: add small subset of SECURITY_PATH hooks to BPF sleepable_lsm_hooks list
    https://git.kernel.org/bpf/bpf-next/c/b13cddf63356

You are awesome, thank you!

Patch

diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
index 7d2f96413a57..63b4dc495125 100644
--- a/kernel/bpf/bpf_lsm.c
+++ b/kernel/bpf/bpf_lsm.c
@@ -304,6 +304,18 @@  BTF_ID(func, bpf_lsm_kernel_module_request)
 BTF_ID(func, bpf_lsm_kernel_read_file)
 BTF_ID(func, bpf_lsm_kernfs_init_security)
 
+#ifdef CONFIG_SECURITY_PATH
+BTF_ID(func, bpf_lsm_path_unlink)
+BTF_ID(func, bpf_lsm_path_mkdir)
+BTF_ID(func, bpf_lsm_path_rmdir)
+BTF_ID(func, bpf_lsm_path_truncate)
+BTF_ID(func, bpf_lsm_path_symlink)
+BTF_ID(func, bpf_lsm_path_link)
+BTF_ID(func, bpf_lsm_path_rename)
+BTF_ID(func, bpf_lsm_path_chmod)
+BTF_ID(func, bpf_lsm_path_chown)
+#endif /* CONFIG_SECURITY_PATH */
+
 #ifdef CONFIG_KEYS
 BTF_ID(func, bpf_lsm_key_free)
 #endif /* CONFIG_KEYS */