On 07/26/2018 12:08 AM, Arthur Fabre wrote: > When check_alu_op() handles a BPF_MOV between two registers, > it calls check_reg_arg() on the dst register, marking it as unbounded. > If the src and dst register are the same, this marks the src as > unbounded, which can lead to unexpected errors for further checks that > rely on bounds info. > > check_alu_op() now only marks the dst register as unbounded if it > different from the src register. > > Signed-off-by: Arthur Fabre <afa...@cloudflare.com> > --- > kernel/bpf/verifier.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > index 63aaac52a265..ddfe3c544a80 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -3238,8 +3238,9 @@ static int check_alu_op(struct bpf_verifier_env > *env, struct bpf_insn *insn) > } > } > > - /* check dest operand */ > - err = check_reg_arg(env, insn->dst_reg, DST_OP); > + /* check dest operand, only mark if dest != src */ > + err = check_reg_arg(env, insn->dst_reg, > + insn->dst_reg == insn->src_reg ? > DST_OP_NO_MARK : DST_OP); > if (err) > return err; >
Thanks a lot for the patch! Looks like it's corrupted wrt newline. Please also add test cases to tools/testing/selftests/bpf/test_verifier.c for the cases of mov64 and mov32 where in each src==dst and src!=dst; mov32 should mark it as unbounded but not former, so would be good to keep tracking that in selftests.
