diff options
| author | Alexei Starovoitov <ast@kernel.org> | 2023-03-02 20:14:43 -0800 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2023-03-03 17:42:20 +0100 |
| commit | 20c09d92faeefb8536f705d3a4629e0dc314c8a1 (patch) | |
| tree | f68b08f9877e6905e1bbcaf90ec85d52bc83cc8e /net/bpf | |
| parent | 8d093b4e95a2a16a2cfcd36869b348a17112fabe (diff) | |
bpf: Introduce kptr_rcu.
The life time of certain kernel structures like 'struct cgroup' is protected by RCU.
Hence it's safe to dereference them directly from __kptr tagged pointers in bpf maps.
The resulting pointer is MEM_RCU and can be passed to kfuncs that expect KF_RCU.
Derefrence of other kptr-s returns PTR_UNTRUSTED.
For example:
struct map_value {
struct cgroup __kptr *cgrp;
};
SEC("tp_btf/cgroup_mkdir")
int BPF_PROG(test_cgrp_get_ancestors, struct cgroup *cgrp_arg, const char *path)
{
struct cgroup *cg, *cg2;
cg = bpf_cgroup_acquire(cgrp_arg); // cg is PTR_TRUSTED and ref_obj_id > 0
bpf_kptr_xchg(&v->cgrp, cg);
cg2 = v->cgrp; // This is new feature introduced by this patch.
// cg2 is PTR_MAYBE_NULL | MEM_RCU.
// When cg2 != NULL, it's a valid cgroup, but its percpu_ref could be zero
if (cg2)
bpf_cgroup_ancestor(cg2, level); // safe to do.
}
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/bpf/20230303041446.3630-4-alexei.starovoitov@gmail.com
Diffstat (limited to 'net/bpf')
| -rw-r--r-- | net/bpf/test_run.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c index 6f3d654b3339..6a8b33a103a4 100644 --- a/net/bpf/test_run.c +++ b/net/bpf/test_run.c @@ -737,6 +737,7 @@ __bpf_kfunc void bpf_kfunc_call_test_mem_len_fail2(u64 *mem, int len) __bpf_kfunc void bpf_kfunc_call_test_ref(struct prog_test_ref_kfunc *p) { + /* p != NULL, but p->cnt could be 0 */ } __bpf_kfunc void bpf_kfunc_call_test_destructive(void) @@ -784,7 +785,7 @@ BTF_ID_FLAGS(func, bpf_kfunc_call_test_fail3) BTF_ID_FLAGS(func, bpf_kfunc_call_test_mem_len_pass1) BTF_ID_FLAGS(func, bpf_kfunc_call_test_mem_len_fail1) BTF_ID_FLAGS(func, bpf_kfunc_call_test_mem_len_fail2) -BTF_ID_FLAGS(func, bpf_kfunc_call_test_ref, KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_kfunc_call_test_ref, KF_TRUSTED_ARGS | KF_RCU) BTF_ID_FLAGS(func, bpf_kfunc_call_test_destructive, KF_DESTRUCTIVE) BTF_ID_FLAGS(func, bpf_kfunc_call_test_static_unused_arg) BTF_SET8_END(test_sk_check_kfunc_ids) |