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| author | Alexei Starovoitov <ast@kernel.org> | 2023-04-04 07:50:26 +0300 |
|---|---|---|
| committer | Andrii Nakryiko <andrii@kernel.org> | 2023-04-05 02:57:18 +0300 |
| commit | add68b843f33d4e5dcbdc7ba6dffe7750a964159 (patch) | |
| tree | f81ce4205a4e3ea44be76de6004b4e5d3b681170 /kernel/bpf | |
| parent | 91571a515d1bcdc280bb46423bb697ea7eb42ff3 (diff) | |
| download | linux-add68b843f33d4e5dcbdc7ba6dffe7750a964159.tar.xz | |
bpf: Refactor NULL-ness check in check_reg_type().
check_reg_type() unconditionally disallows PTR_TO_BTF_ID | PTR_MAYBE_NULL.
It's problematic for helpers that allow ARG_PTR_TO_BTF_ID_OR_NULL like
bpf_sk_storage_get(). Allow passing PTR_TO_BTF_ID | PTR_MAYBE_NULL into such
helpers. That technically includes bpf_kptr_xchg() helper, but in practice:
bpf_kptr_xchg(..., bpf_cpumask_create());
is still disallowed because bpf_cpumask_create() returns ref counted pointer
with ref_obj_id > 0.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/bpf/20230404045029.82870-6-alexei.starovoitov@gmail.com
Diffstat (limited to 'kernel/bpf')
| -rw-r--r-- | kernel/bpf/verifier.c | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 2cd2e0b725cd..4e7d671497f4 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -7168,6 +7168,8 @@ found: case PTR_TO_BTF_ID: case PTR_TO_BTF_ID | PTR_TRUSTED: case PTR_TO_BTF_ID | MEM_RCU: + case PTR_TO_BTF_ID | PTR_MAYBE_NULL: + case PTR_TO_BTF_ID | PTR_MAYBE_NULL | MEM_RCU: { /* For bpf_sk_release, it needs to match against first member * 'struct sock_common', hence make an exception for it. This @@ -7176,6 +7178,12 @@ found: bool strict_type_match = arg_type_is_release(arg_type) && meta->func_id != BPF_FUNC_sk_release; + if (type_may_be_null(reg->type) && + (!type_may_be_null(arg_type) || arg_type_is_release(arg_type))) { + verbose(env, "Possibly NULL pointer passed to helper arg%d\n", regno); + return -EACCES; + } + if (!arg_btf_id) { if (!compatible->btf_id) { verbose(env, "verifier internal error: missing arg compatible BTF ID\n"); @@ -7206,10 +7214,6 @@ found: } break; } - case PTR_TO_BTF_ID | PTR_MAYBE_NULL: - case PTR_TO_BTF_ID | PTR_MAYBE_NULL | MEM_RCU: - verbose(env, "Possibly NULL pointer passed to helper arg%d\n", regno); - return -EACCES; case PTR_TO_BTF_ID | MEM_ALLOC: if (meta->func_id != BPF_FUNC_spin_lock && meta->func_id != BPF_FUNC_spin_unlock && meta->func_id != BPF_FUNC_kptr_xchg) { |