| Message ID | 20230424204321.2680232-1-davemarchevsky@fb.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 7deca5eae83389ca40ac1b1bde96e4af17cca84f |
| Delegated to: | BPF |
| Headers | show |
| Series | [v2,bpf-next] bpf: Disable bpf_refcount_acquire kfunc calls until race conditions are fixed | expand |
Hello: This patch was applied to bpf/bpf-next.git (master) by Alexei Starovoitov <ast@kernel.org>: On Mon, 24 Apr 2023 13:43:21 -0700 you wrote: > As reported by Kumar in [0], the shared ownership implementation for BPF > programs has some race conditions which need to be addressed before it > can safely be used. This patch does so in a minimal way instead of > ripping out shared ownership entirely, as proper fixes for the issues > raised will follow ASAP, at which point this patch's commit can be > reverted to re-enable shared ownership. > > [...] Here is the summary with links: - [v2,bpf-next] bpf: Disable bpf_refcount_acquire kfunc calls until race conditions are fixed https://git.kernel.org/bpf/bpf-next/c/7deca5eae833 You are awesome, thank you!
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 0d73139ee4d8..5c4aa393f65a 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -10509,7 +10509,10 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ verbose(env, "arg#%d doesn't point to a type with bpf_refcount field\n", i); return -EINVAL; } - + if (rec->refcount_off >= 0) { + verbose(env, "bpf_refcount_acquire calls are disabled for now\n"); + return -EINVAL; + } meta->arg_refcount_acquire.btf = reg->btf; meta->arg_refcount_acquire.btf_id = reg->btf_id; break; diff --git a/tools/testing/selftests/bpf/prog_tests/refcounted_kptr.c b/tools/testing/selftests/bpf/prog_tests/refcounted_kptr.c index 2ab23832062d..595cbf92bff5 100644 --- a/tools/testing/selftests/bpf/prog_tests/refcounted_kptr.c +++ b/tools/testing/selftests/bpf/prog_tests/refcounted_kptr.c @@ -9,10 +9,8 @@ void test_refcounted_kptr(void) { - RUN_TESTS(refcounted_kptr); } void test_refcounted_kptr_fail(void) { - RUN_TESTS(refcounted_kptr_fail); }
As reported by Kumar in [0], the shared ownership implementation for BPF programs has some race conditions which need to be addressed before it can safely be used. This patch does so in a minimal way instead of ripping out shared ownership entirely, as proper fixes for the issues raised will follow ASAP, at which point this patch's commit can be reverted to re-enable shared ownership. The patch removes the ability to call bpf_refcount_acquire_impl from BPF programs. Programs can only bump refcount and obtain a new owning reference using this kfunc, so removing the ability to call it effectively disables shared ownership. Instead of changing success / failure expectations for bpf_refcount-related selftests, this patch just disables them from running for now. [0]: https://lore.kernel.org/bpf/d7hyspcow5wtjcmw4fugdgyp3fwhljwuscp3xyut5qnwivyeru@ysdq543otzv2/ Reported-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com> --- kernel/bpf/verifier.c | 5 ++++- tools/testing/selftests/bpf/prog_tests/refcounted_kptr.c | 2 -- 2 files changed, 4 insertions(+), 3 deletions(-)