On Thu, Nov 11, 2021 at 8:16 AM Lorenz Bauer <lmb@xxxxxxxxxxxxxx> wrote: > > Ensure that two registers with a map_value loaded from a nested > map are considered equivalent for the purpose of state pruning > and don't cause the verifier to revisit a pruning point. > > This uses a rather crude match on the number of insns visited by > the verifier, which might change in the future. I've therefore > tried to keep the code as "unpruneable" as possible by having > the code paths only converge on the second to last instruction. > > Should you require to adjust the test in the future, reducing the > number of processed instructions should always be safe. Increasing > them could cause another regression, so proceed with caution. > > Suggested-by: Alexei Starovoitov <ast@xxxxxxxxxx> > Signed-off-by: Lorenz Bauer <lmb@xxxxxxxxxxxxxx> > Link: https://lore.kernel.org/bpf/CACAyw99hVEJFoiBH_ZGyy=+oO-jyydoz6v1DeKPKs2HVsUH28w@xxxxxxxxxxxxxx/ > --- > .../selftests/bpf/verifier/map_in_map.c | 33 +++++++++++++++++++ > 1 file changed, 33 insertions(+) > > diff --git a/tools/testing/selftests/bpf/verifier/map_in_map.c b/tools/testing/selftests/bpf/verifier/map_in_map.c > index 2798927ee9ff..f46c7121e216 100644 > --- a/tools/testing/selftests/bpf/verifier/map_in_map.c > +++ b/tools/testing/selftests/bpf/verifier/map_in_map.c > @@ -18,6 +18,39 @@ > .fixup_map_in_map = { 3 }, > .result = ACCEPT, > }, > +{ > + "map in map state pruning", > + .insns = { > + BPF_ST_MEM(0, BPF_REG_10, -4, 0), > + BPF_MOV64_REG(BPF_REG_6, BPF_REG_10), > + BPF_ALU64_IMM(BPF_ADD, BPF_REG_6, -4), > + BPF_MOV64_REG(BPF_REG_2, BPF_REG_6), > + BPF_LD_MAP_FD(BPF_REG_1, 0), > + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), > + BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1), > + BPF_EXIT_INSN(), > + BPF_MOV64_REG(BPF_REG_2, BPF_REG_6), > + BPF_MOV64_REG(BPF_REG_1, BPF_REG_0), > + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), > + BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 11), > + BPF_MOV64_REG(BPF_REG_2, BPF_REG_6), > + BPF_LD_MAP_FD(BPF_REG_1, 0), > + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), > + BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1), > + BPF_EXIT_INSN(), > + BPF_MOV64_REG(BPF_REG_2, BPF_REG_6), > + BPF_MOV64_REG(BPF_REG_1, BPF_REG_0), > + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem), > + BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1), > + BPF_EXIT_INSN(), > + BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_0, 0), > + BPF_EXIT_INSN(), > + }, > + .fixup_map_in_map = { 4, 14 }, > + .flags = BPF_F_TEST_STATE_FREQ, > + .result = VERBOSE_ACCEPT, > + .errstr = "processed 25 insns", > +}, Not sure how you've tested it, but it doesn't work in unpriv: $ test_verifier 789 #789/u map in map state pruning FAIL processed 26 insns (limit 1000000) max_states_per_insn 0 total_states 2 peak_states 2 mark_read 1 #789/p map in map state pruning OK I've added .prog_type = BPF_PROG_TYPE_XDP, and force pushed.
