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| author | Alexei Starovoitov <ast@kernel.org> | 2022-11-24 13:53:14 -0800 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2022-11-24 23:47:09 +0100 |
| commit | c6b0337f01205decb31ed5e90e5aa760ac2d5b41 (patch) | |
| tree | 96f3d431dcf81055a62e168ae8b241893132a77a /kernel/bpf | |
| parent | 6099754a1493467d2db15a20756e32e9a69c2cec (diff) | |
| download | linux-c6b0337f01205decb31ed5e90e5aa760ac2d5b41.tar.gz linux-c6b0337f01205decb31ed5e90e5aa760ac2d5b41.tar.bz2 linux-c6b0337f01205decb31ed5e90e5aa760ac2d5b41.zip | |
bpf: Don't mark arguments to fentry/fexit programs as trusted.
The PTR_TRUSTED flag should only be applied to pointers where the verifier can
guarantee that such pointers are valid.
The fentry/fexit/fmod_ret programs are not in this category.
Only arguments of SEC("tp_btf") and SEC("iter") programs are trusted
(which have BPF_TRACE_RAW_TP and BPF_TRACE_ITER attach_type correspondingly)
This bug was masked because convert_ctx_accesses() was converting trusted
loads into BPF_PROBE_MEM loads. Fix it as well.
The loads from trusted pointers don't need exception handling.
Fixes: 3f00c5239344 ("bpf: Allow trusted pointers to be passed to KF_TRUSTED_ARGS kfuncs")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20221124215314.55890-1-alexei.starovoitov@gmail.com
Diffstat (limited to 'kernel/bpf')
| -rw-r--r-- | kernel/bpf/btf.c | 16 | ||||
| -rw-r--r-- | kernel/bpf/verifier.c | 3 |
2 files changed, 13 insertions, 6 deletions
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index bd3369100239..d11cbf8cece7 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -5821,9 +5821,19 @@ static u32 get_ctx_arg_idx(struct btf *btf, const struct btf_type *func_proto, return nr_args + 1; } -static bool prog_type_args_trusted(enum bpf_prog_type prog_type) +static bool prog_args_trusted(const struct bpf_prog *prog) { - return prog_type == BPF_PROG_TYPE_TRACING || prog_type == BPF_PROG_TYPE_STRUCT_OPS; + enum bpf_attach_type atype = prog->expected_attach_type; + + switch (prog->type) { + case BPF_PROG_TYPE_TRACING: + return atype == BPF_TRACE_RAW_TP || atype == BPF_TRACE_ITER; + case BPF_PROG_TYPE_LSM: + case BPF_PROG_TYPE_STRUCT_OPS: + return true; + default: + return false; + } } bool btf_ctx_access(int off, int size, enum bpf_access_type type, @@ -5969,7 +5979,7 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type, } info->reg_type = PTR_TO_BTF_ID; - if (prog_type_args_trusted(prog->type)) + if (prog_args_trusted(prog)) info->reg_type |= PTR_TRUSTED; if (tgt_prog) { diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index f4500479f1c2..6599d25dae38 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -14905,7 +14905,6 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env) break; case PTR_TO_BTF_ID: case PTR_TO_BTF_ID | PTR_UNTRUSTED: - case PTR_TO_BTF_ID | PTR_TRUSTED: /* PTR_TO_BTF_ID | MEM_ALLOC always has a valid lifetime, unlike * PTR_TO_BTF_ID, and an active ref_obj_id, but the same cannot * be said once it is marked PTR_UNTRUSTED, hence we must handle @@ -14913,8 +14912,6 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env) * for this case. */ case PTR_TO_BTF_ID | MEM_ALLOC | PTR_UNTRUSTED: - case PTR_TO_BTF_ID | PTR_UNTRUSTED | PTR_TRUSTED: - case PTR_TO_BTF_ID | PTR_UNTRUSTED | MEM_ALLOC | PTR_TRUSTED: if (type == BPF_READ) { insn->code = BPF_LDX | BPF_PROBE_MEM | BPF_SIZE((insn)->code); |