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author | Alexei Starovoitov <ast@kernel.org> | 2023-03-02 20:14:42 -0800 |
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committer | Daniel Borkmann <daniel@iogearbox.net> | 2023-03-03 17:42:20 +0100 |
commit | 8d093b4e95a2a16a2cfcd36869b348a17112fabe (patch) | |
tree | 76ee3f72594b752b3e289117a586312d1e50f051 /kernel/bpf | |
parent | 03b77e17aeb22a5935ea20d585ca6a1f2947e62b (diff) | |
download | linux-stable-8d093b4e95a2a16a2cfcd36869b348a17112fabe.tar.gz linux-stable-8d093b4e95a2a16a2cfcd36869b348a17112fabe.tar.bz2 linux-stable-8d093b4e95a2a16a2cfcd36869b348a17112fabe.zip |
bpf: Mark cgroups and dfl_cgrp fields as trusted.
bpf programs sometimes do:
bpf_cgrp_storage_get(&map, task->cgroups->dfl_cgrp, ...);
It is safe to do, because cgroups->dfl_cgrp pointer is set diring init and
never changes. The task->cgroups is also never NULL. It is also set during init
and will change when task switches cgroups. For any trusted task pointer
dereference of cgroups and dfl_cgrp should yield trusted pointers. The verifier
wasn't aware of this. Hence in gcc compiled kernels task->cgroups dereference
was producing PTR_TO_BTF_ID without modifiers while in clang compiled kernels
the verifier recognizes __rcu tag in cgroups field and produces
PTR_TO_BTF_ID | MEM_RCU | MAYBE_NULL.
Tag cgroups and dfl_cgrp as trusted to equalize clang and gcc behavior.
When GCC supports btf_type_tag such tagging will done directly in the type.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: David Vernet <void@manifault.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/bpf/20230303041446.3630-3-alexei.starovoitov@gmail.com
Diffstat (limited to 'kernel/bpf')
-rw-r--r-- | kernel/bpf/verifier.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index bf580f246a01..b834f3d2d81a 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -5046,6 +5046,11 @@ static int bpf_map_direct_read(struct bpf_map *map, int off, int size, u64 *val) BTF_TYPE_SAFE_NESTED(struct task_struct) { const cpumask_t *cpus_ptr; + struct css_set __rcu *cgroups; +}; + +BTF_TYPE_SAFE_NESTED(struct css_set) { + struct cgroup *dfl_cgrp; }; static bool nested_ptr_is_trusted(struct bpf_verifier_env *env, @@ -5057,6 +5062,7 @@ static bool nested_ptr_is_trusted(struct bpf_verifier_env *env, return false; BTF_TYPE_EMIT(BTF_TYPE_SAFE_NESTED(struct task_struct)); + BTF_TYPE_EMIT(BTF_TYPE_SAFE_NESTED(struct css_set)); return btf_nested_type_is_trusted(&env->log, reg, off); } |