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| author | Toke Høiland-Jørgensen <toke@redhat.com> | 2020-09-25 23:25:00 +0200 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2020-09-28 17:08:07 -0700 |
| commit | 1af9270e908cd50a4f5d815c9b6f794c7d57ed07 (patch) | |
| tree | 74df99b5438c997caf6158e6a7e8afcc1e903e46 /kernel/bpf | |
| parent | 84a20d8e8795b45e3f1673648d43b4cf0f594359 (diff) | |
| download | linux-1af9270e908cd50a4f5d815c9b6f794c7d57ed07.tar.bz2 | |
bpf: disallow attaching modify_return tracing functions to other BPF programs
From the checks and commit messages for modify_return, it seems it was
never the intention that it should be possible to attach a tracing program
with expected_attach_type == BPF_MODIFY_RETURN to another BPF program.
However, check_attach_modify_return() will only look at the function name,
so if the target function starts with "security_", the attach will be
allowed even for bpf2bpf attachment.
Fix this oversight by also blocking the modification if a target program is
supplied.
Fixes: 18644cec714a ("bpf: Fix use-after-free in fmod_ret check")
Fixes: 6ba43b761c41 ("bpf: Attachment verification for BPF_MODIFY_RETURN")
Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/bpf')
| -rw-r--r-- | kernel/bpf/verifier.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index cc9c90d74dc1..52649a5497ce 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -11500,6 +11500,11 @@ static int check_attach_btf_id(struct bpf_verifier_env *env) verbose(env, "%s is not sleepable\n", prog->aux->attach_func_name); } else if (prog->expected_attach_type == BPF_MODIFY_RETURN) { + if (tgt_prog) { + verbose(env, "can't modify return codes of BPF programs\n"); + ret = -EINVAL; + goto out; + } ret = check_attach_modify_return(prog, addr); if (ret) verbose(env, "%s() is not modifiable\n", |