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| author | Dave Marchevsky <davemarchevsky@fb.com> | 2023-11-07 09:56:34 +0100 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2023-11-10 04:07:51 +0100 |
| commit | 1500a5d9f49cb66906d3ea1c9158df25cc41dd40 (patch) | |
| tree | e0fbb55fc5153e5187e424e4db11f2eb5aa889f4 | |
| parent | bpf: replace register_is_const() with is_reg_const() (diff) | |
| download | linux-1500a5d9f49cb66906d3ea1c9158df25cc41dd40.tar.xz linux-1500a5d9f49cb66906d3ea1c9158df25cc41dd40.zip | |
bpf: Add KF_RCU flag to bpf_refcount_acquire_impl
Refcounted local kptrs are kptrs to user-defined types with a
bpf_refcount field. Recent commits ([0], [1]) modified the lifetime of
refcounted local kptrs such that the underlying memory is not reused
until RCU grace period has elapsed.
Separately, verification of bpf_refcount_acquire calls currently
succeeds for MAYBE_NULL non-owning reference input, which is a problem
as bpf_refcount_acquire_impl has no handling for this case.
This patch takes advantage of aforementioned lifetime changes to tag
bpf_refcount_acquire_impl kfunc KF_RCU, thereby preventing MAYBE_NULL
input to the kfunc. The KF_RCU flag applies to all kfunc params; it's
fine for it to apply to the void *meta__ign param as that's populated by
the verifier and is tagged __ign regardless.
[0]: commit 7e26cd12ad1c ("bpf: Use bpf_mem_free_rcu when
bpf_obj_dropping refcounted nodes") is the actual change to
allocation behaivor
[1]: commit 0816b8c6bf7f ("bpf: Consider non-owning refs to refcounted
nodes RCU protected") modified verifier understanding of
refcounted local kptrs to match [0]'s changes
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Fixes: 7c50b1cb76ac ("bpf: Add bpf_refcount_acquire kfunc")
Link: https://lore.kernel.org/r/20231107085639.3016113-2-davemarchevsky@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
| -rw-r--r-- | kernel/bpf/helpers.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 174f02a9e703..b84d8cb8d239 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2520,7 +2520,7 @@ BTF_ID_FLAGS(func, bpf_obj_new_impl, KF_ACQUIRE | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_percpu_obj_new_impl, KF_ACQUIRE | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_obj_drop_impl, KF_RELEASE) BTF_ID_FLAGS(func, bpf_percpu_obj_drop_impl, KF_RELEASE) -BTF_ID_FLAGS(func, bpf_refcount_acquire_impl, KF_ACQUIRE | KF_RET_NULL) +BTF_ID_FLAGS(func, bpf_refcount_acquire_impl, KF_ACQUIRE | KF_RET_NULL | KF_RCU) BTF_ID_FLAGS(func, bpf_list_push_front_impl) BTF_ID_FLAGS(func, bpf_list_push_back_impl) BTF_ID_FLAGS(func, bpf_list_pop_front, KF_ACQUIRE | KF_RET_NULL) |