bpf: improve verifier packet range checks
llvm can optimize the 'if (ptr > data_end)' checks to be in the order
slightly different than the original C code which will confuse verifier.
Like:
if (ptr + 16 > data_end)
return TC_ACT_SHOT;
// may be followed by
if (ptr + 14 > data_end)
return TC_ACT_SHOT;
while llvm can see that 'ptr' is valid for all 16 bytes,
the verifier could not.
Fix verifier logic to account for such case and add a test.
Reported-by: Huapeng Zhou <hzhou@fb.com>
Fixes: 969bf05eb3
("bpf: direct packet access")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Родитель
43a6684519
Коммит
b1977682a3
|
@ -1973,14 +1973,15 @@ static void find_good_pkt_pointers(struct bpf_verifier_state *state,
|
|||
|
||||
for (i = 0; i < MAX_BPF_REG; i++)
|
||||
if (regs[i].type == PTR_TO_PACKET && regs[i].id == dst_reg->id)
|
||||
regs[i].range = dst_reg->off;
|
||||
/* keep the maximum range already checked */
|
||||
regs[i].range = max(regs[i].range, dst_reg->off);
|
||||
|
||||
for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
|
||||
if (state->stack_slot_type[i] != STACK_SPILL)
|
||||
continue;
|
||||
reg = &state->spilled_regs[i / BPF_REG_SIZE];
|
||||
if (reg->type == PTR_TO_PACKET && reg->id == dst_reg->id)
|
||||
reg->range = dst_reg->off;
|
||||
reg->range = max(reg->range, dst_reg->off);
|
||||
}
|
||||
}
|
||||
|
||||
|
|
|
@ -3417,6 +3417,26 @@ static struct bpf_test tests[] = {
|
|||
.result = ACCEPT,
|
||||
.prog_type = BPF_PROG_TYPE_LWT_XMIT,
|
||||
},
|
||||
{
|
||||
"overlapping checks for direct packet access",
|
||||
.insns = {
|
||||
BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1,
|
||||
offsetof(struct __sk_buff, data)),
|
||||
BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_1,
|
||||
offsetof(struct __sk_buff, data_end)),
|
||||
BPF_MOV64_REG(BPF_REG_0, BPF_REG_2),
|
||||
BPF_ALU64_IMM(BPF_ADD, BPF_REG_0, 8),
|
||||
BPF_JMP_REG(BPF_JGT, BPF_REG_0, BPF_REG_3, 4),
|
||||
BPF_MOV64_REG(BPF_REG_1, BPF_REG_2),
|
||||
BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, 6),
|
||||
BPF_JMP_REG(BPF_JGT, BPF_REG_1, BPF_REG_3, 1),
|
||||
BPF_LDX_MEM(BPF_H, BPF_REG_0, BPF_REG_2, 6),
|
||||
BPF_MOV64_IMM(BPF_REG_0, 0),
|
||||
BPF_EXIT_INSN(),
|
||||
},
|
||||
.result = ACCEPT,
|
||||
.prog_type = BPF_PROG_TYPE_LWT_XMIT,
|
||||
},
|
||||
{
|
||||
"invalid access of tc_classid for LWT_IN",
|
||||
.insns = {
|
||||
|
|
Загрузка…
Ссылка в новой задаче