diff options
| author | John Fastabend <john.fastabend@gmail.com> | 2020-06-24 15:20:39 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-07-16 08:13:18 +0200 |
| commit | 82d1d58e9f2070b0055f29480ab43b629cb280ef (patch) | |
| tree | 7d22a6510f834c5b9399c035a21e8e0151fe1e93 /kernel | |
| parent | 719a2cc571b8bce1c25ce61ca10d0811bfc6de62 (diff) | |
bpf: Do not allow btf_ctx_access with __int128 types
[ Upstream commit a9b59159d338d414acaa8e2f569d129d51c76452 ]
To ensure btf_ctx_access() is safe the verifier checks that the BTF
arg type is an int, enum, or pointer. When the function does the
BTF arg lookup it uses the calculation 'arg = off / 8' using the
fact that registers are 8B. This requires that the first arg is
in the first reg, the second in the second, and so on. However,
for __int128 the arg will consume two registers by default LLVM
implementation. So this will cause the arg layout assumed by the
'arg = off / 8' calculation to be incorrect.
Because __int128 is uncommon this patch applies the easiest fix and
will force int types to be sizeof(u64) or smaller so that they will
fit in a single register.
v2: remove unneeded parens per Andrii's feedback
Fixes: 9e15db66136a1 ("bpf: Implement accurate raw_tp context access via BTF")
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/159303723962.11287.13309537171132420717.stgit@john-Precision-5820-Tower
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/bpf/btf.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index d65c6912bdaf..d1f5d428c9fe 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -3744,7 +3744,7 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type, return false; t = btf_type_skip_modifiers(btf, t->type, NULL); - if (!btf_type_is_int(t)) { + if (!btf_type_is_small_int(t)) { bpf_log(log, "ret type %s not allowed for fmod_ret\n", btf_kind_str[BTF_INFO_KIND(t->info)]); @@ -3766,7 +3766,7 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type, /* skip modifiers */ while (btf_type_is_modifier(t)) t = btf_type_by_id(btf, t->type); - if (btf_type_is_int(t) || btf_type_is_enum(t)) + if (btf_type_is_small_int(t) || btf_type_is_enum(t)) /* accessing a scalar */ return true; if (!btf_type_is_ptr(t)) { |