Currently, the verifier does not handle '<const> <cond_op> <non_const>' well.
For example,
...
10: (79) r1 = *(u64 *)(r10 -16) ; R1_w=scalar() R10=fp0
11: (b7) r2 = 0 ; R2_w=0
12: (2d) if r2 > r1 goto pc+2
13: (b7) r0 = 0
14: (95) exit
15: (65) if r1 s> 0x1 goto pc+3
16: (0f) r0 += r1
...
At insn 12, verifier decides both true and false branch are possible, but
actually only false branch is possible.
Currently, the verifier already supports patterns '<non_const> <cond_op> <const>.
Add support for patterns '<const> <cond_op> <non_const>' in a similar way.
Also fix selftest 'verifier_bounds_mix_sign_unsign/bounds checks mixing signed and unsigned, variant 10'
due to this change.
Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Dave Marchevsky <davemarchevsky@fb.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230406164505.1046801-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
src_reg->var_off.value,
opcode,
is_jmp32);
+ } else if (dst_reg->type == SCALAR_VALUE &&
+ is_jmp32 && tnum_is_const(tnum_subreg(dst_reg->var_off))) {
+ pred = is_branch_taken(src_reg,
+ tnum_subreg(dst_reg->var_off).value,
+ flip_opcode(opcode),
+ is_jmp32);
+ } else if (dst_reg->type == SCALAR_VALUE &&
+ !is_jmp32 && tnum_is_const(dst_reg->var_off)) {
+ pred = is_branch_taken(src_reg,
+ dst_reg->var_off.value,
+ flip_opcode(opcode),
+ is_jmp32);
} else if (reg_is_pkt_pointer_any(dst_reg) &&
reg_is_pkt_pointer_any(src_reg) &&
!is_jmp32) {
call %[bpf_map_lookup_elem]; \
if r0 == 0 goto l0_%=; \
r1 = *(u64*)(r10 - 16); \
- r2 = 0; \
+ r2 = -1; \
if r2 > r1 goto l1_%=; \
r0 = 0; \
exit; \