On 11/28/18 3:45 AM, Daniel Borkmann wrote:
On 11/28/2018 08:51 AM, Prashant Bhole wrote:This patch adds tests to check whether bpf verifier prevents lookup on queue/stack maps Signed-off-by: Prashant Bhole <bhole_prashant...@lab.ntt.co.jp> --- tools/testing/selftests/bpf/test_verifier.c | 52 +++++++++++++++++++++ 1 file changed, 52 insertions(+) diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c index 550b7e46bf4a..becd9f4f3980 100644 --- a/tools/testing/selftests/bpf/test_verifier.c +++ b/tools/testing/selftests/bpf/test_verifier.c @@ -74,6 +74,8 @@ struct bpf_test { int fixup_map_in_map[MAX_FIXUPS]; int fixup_cgroup_storage[MAX_FIXUPS]; int fixup_percpu_cgroup_storage[MAX_FIXUPS]; + int fixup_map_queue[MAX_FIXUPS]; + int fixup_map_stack[MAX_FIXUPS]; const char *errstr; const char *errstr_unpriv; uint32_t retval, retval_unpriv; @@ -4611,6 +4613,38 @@ static struct bpf_test tests[] = { .errstr = "cannot pass map_type 7 into func bpf_map_lookup_elem", .prog_type = BPF_PROG_TYPE_PERF_EVENT, }, + { + "prevent map lookup in queue map", + .insns = { + BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0), + BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), + BPF_LD_MAP_FD(BPF_REG_1, 0), + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, + BPF_FUNC_map_lookup_elem), + BPF_EXIT_INSN(), + }, + .fixup_map_queue = { 3 }, + .result = REJECT, + .errstr = "invalid stack type R2 off=-8 access_size=0", + .prog_type = BPF_PROG_TYPE_XDP,Hmm, the approach in patch 1 is very fragile, and we're lucky in this case that the verifier bailed out with 'invalid stack type R2 off=-8 access_size=0' because of key size being zero. If this would have not been the case then the added ERR_PTR(-EOPNOTSUPP) would basically be seen as a valid pointer and the program could read/write into it. Instead, this needs to be prevented much earlier like check_map_func_compatibility(),
Actually it is prevented in check_map_func_compatibility(), but stack boundary check is done before in the verifier.
and I would like to have a split on these approaches to make verifier more robust. While you want ERR_PTR(-EOPNOTSUPP) for user space syscall side,
In the case of QUEUE and STACK maps this is not relevant because the lookup syscall is mapped into peek operation.
In fact queue_stack_map_lookup_elem() & queue_stack_map_update_elem() should be never called, I think we can remove them safely.
Mauricio.
the BPF prog should only ever see (if anything) a NULL here, because this is what the verifier matches later on to set the map value_or_null pointer to a map value pointer.+ }, + { + "prevent map lookup in stack map", + .insns = { + BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0), + BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), + BPF_LD_MAP_FD(BPF_REG_1, 0), + BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, + BPF_FUNC_map_lookup_elem), + BPF_EXIT_INSN(), + }, + .fixup_map_stack = { 3 }, + .result = REJECT, + .errstr = "invalid stack type R2 off=-8 access_size=0", + .prog_type = BPF_PROG_TYPE_XDP, + }, { "prevent map lookup in prog array", .insns = { @@ -14048,6 +14082,8 @@ static void do_test_fixup(struct bpf_test *test, enum bpf_map_type prog_type, int *fixup_map_sockhash = test->fixup_map_sockhash; int *fixup_map_xskmap = test->fixup_map_xskmap; int *fixup_map_stacktrace = test->fixup_map_stacktrace; + int *fixup_map_queue = test->fixup_map_queue; + int *fixup_map_stack = test->fixup_map_stack; int *fixup_prog1 = test->fixup_prog1; int *fixup_prog2 = test->fixup_prog2; int *fixup_map_in_map = test->fixup_map_in_map; @@ -14168,6 +14204,22 @@ static void do_test_fixup(struct bpf_test *test, enum bpf_map_type prog_type, fixup_map_stacktrace++; } while (fixup_map_stacktrace); } + if (*fixup_map_queue) { + map_fds[13] = create_map(BPF_MAP_TYPE_QUEUE, 0, + sizeof(u32), 1); + do { + prog[*fixup_map_queue].imm = map_fds[13]; + fixup_map_queue++; + } while (*fixup_map_queue); + } + if (*fixup_map_stack) { + map_fds[14] = create_map(BPF_MAP_TYPE_STACK, 0, + sizeof(u32), 1); + do { + prog[*fixup_map_stack].imm = map_fds[14]; + fixup_map_stack++; + } while (*fixup_map_stack); + } }static int set_admin(bool admin)
