diff options
| author | Shung-Hsi Yu <shung-hsi.yu@suse.com> | 2023-11-02 13:39:03 +0800 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2023-11-01 22:54:27 -0700 |
| commit | 291d044fd51f8484066300ee42afecf8c8db7b3a (patch) | |
| tree | c89109320ecb69c5eea9fdb3cd4580dbf031ddae /kernel/bpf | |
| parent | 698b8c5e3b5505ac00102caf9e4843b71192b586 (diff) | |
bpf: Fix precision tracking for BPF_ALU | BPF_TO_BE | BPF_END
BPF_END and BPF_NEG has a different specification for the source bit in
the opcode compared to other ALU/ALU64 instructions, and is either
reserved or use to specify the byte swap endianness. In both cases the
source bit does not encode source operand location, and src_reg is a
reserved field.
backtrack_insn() currently does not differentiate BPF_END and BPF_NEG
from other ALU/ALU64 instructions, which leads to r0 being incorrectly
marked as precise when processing BPF_ALU | BPF_TO_BE | BPF_END
instructions. This commit teaches backtrack_insn() to correctly mark
precision for such case.
While precise tracking of BPF_NEG and other BPF_END instructions are
correct and does not need fixing, this commit opt to process all BPF_NEG
and BPF_END instructions within the same if-clause to better align with
current convention used in the verifier (e.g. check_alu_op).
Fixes: b5dc0163d8fd ("bpf: precise scalar_value tracking")
Cc: stable@vger.kernel.org
Reported-by: Mohamed Mahmoud <mmahmoud@redhat.com>
Closes: https://lore.kernel.org/r/87jzrrwptf.fsf@toke.dk
Tested-by: Toke Høiland-Jørgensen <toke@redhat.com>
Tested-by: Tao Lyu <tao.lyu@epfl.ch>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
Link: https://lore.kernel.org/r/20231102053913.12004-2-shung-hsi.yu@suse.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/bpf')
| -rw-r--r-- | kernel/bpf/verifier.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index def99b1a2b17..bd1c42eb540f 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3742,7 +3742,12 @@ static int backtrack_insn(struct bpf_verifier_env *env, int idx, int subseq_idx, if (class == BPF_ALU || class == BPF_ALU64) { if (!bt_is_reg_set(bt, dreg)) return 0; - if (opcode == BPF_MOV) { + if (opcode == BPF_END || opcode == BPF_NEG) { + /* sreg is reserved and unused + * dreg still need precision before this insn + */ + return 0; + } else if (opcode == BPF_MOV) { if (BPF_SRC(insn->code) == BPF_X) { /* dreg = sreg or dreg = (s8, s16, s32)sreg * dreg needs precision after this insn |