selftests/bpf: add test for bogus operations on pointers

Tests non-add/sub operations (AND, LSH) on pointers decaying them to
 unknown scalars.
Also tests that a pkt_ptr add which could potentially overflow is rejected
 (find_good_pkt_pointers ignores it and doesn't give us any reg->range).

Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/tools/testing/selftests/bpf/test_align.c b/tools/testing/selftests/bpf/test_align.c
index 74cc4a6..b081683 100644 (file)
--- a/tools/testing/selftests/bpf/test_align.c
+++ b/tools/testing/selftests/bpf/test_align.c
@@ -441,6 +441,62 @@ static struct bpf_align_test tests[] = {
                        {23, "R5=pkt(id=2,off=0,r=4,umin_value=14,umax_value=2054,var_off=(0x2; 0xffc))"},
                },
        },
+       {
+               .descr = "dubious pointer arithmetic",
+               .insns = {
+                       PREP_PKT_POINTERS,
+                       BPF_MOV64_IMM(BPF_REG_0, 0),
+                       /* ptr & const => unknown & const */
+                       BPF_MOV64_REG(BPF_REG_5, BPF_REG_2),
+                       BPF_ALU64_IMM(BPF_AND, BPF_REG_5, 0x40),
+                       /* ptr << const => unknown << const */
+                       BPF_MOV64_REG(BPF_REG_5, BPF_REG_2),
+                       BPF_ALU64_IMM(BPF_LSH, BPF_REG_5, 2),
+                       /* We have a (4n) value.  Let's make a packet offset
+                        * out of it.  First add 14, to make it a (4n+2)
+                        */
+                       BPF_ALU64_IMM(BPF_ADD, BPF_REG_5, 14),
+                       /* Then make sure it's nonnegative */
+                       BPF_JMP_IMM(BPF_JSGE, BPF_REG_5, 0, 1),
+                       BPF_EXIT_INSN(),
+                       /* Add it to packet pointer */
+                       BPF_MOV64_REG(BPF_REG_6, BPF_REG_2),
+                       BPF_ALU64_REG(BPF_ADD, BPF_REG_6, BPF_REG_5),
+                       /* Check bounds and perform a read */
+                       BPF_MOV64_REG(BPF_REG_4, BPF_REG_6),
+                       BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, 4),
+                       BPF_JMP_REG(BPF_JGE, BPF_REG_3, BPF_REG_4, 1),
+                       BPF_EXIT_INSN(),
+                       BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_6, 0),
+                       BPF_EXIT_INSN(),
+               },
+               .prog_type = BPF_PROG_TYPE_SCHED_CLS,
+               .result = REJECT,
+               .matches = {
+                       {4, "R5=pkt(id=0,off=0,r=0,imm=0)"},
+                       /* ptr & 0x40 == either 0 or 0x40 */
+                       {5, "R5=inv(id=0,umax_value=64,var_off=(0x0; 0x40))"},
+                       /* ptr << 2 == unknown, (4n) */
+                       {7, "R5=inv(id=0,smax_value=9223372036854775804,umax_value=18446744073709551612,var_off=(0x0; 0xfffffffffffffffc))"},
+                       /* (4n) + 14 == (4n+2).  We blow our bounds, because
+                        * the add could overflow.
+                        */
+                       {8, "R5=inv(id=0,var_off=(0x2; 0xfffffffffffffffc))"},
+                       /* Checked s>=0 */
+                       {10, "R5=inv(id=0,umin_value=2,umax_value=9223372036854775806,var_off=(0x2; 0x7ffffffffffffffc))"},
+                       /* packet pointer + nonnegative (4n+2) */
+                       {12, "R6=pkt(id=1,off=0,r=0,umin_value=2,umax_value=9223372036854775806,var_off=(0x2; 0x7ffffffffffffffc))"},
+                       {14, "R4=pkt(id=1,off=4,r=0,umin_value=2,umax_value=9223372036854775806,var_off=(0x2; 0x7ffffffffffffffc))"},
+                       /* NET_IP_ALIGN + (4n+2) == (4n), alignment is fine.
+                        * We checked the bounds, but it might have been able
+                        * to overflow if the packet pointer started in the
+                        * upper half of the address space.
+                        * So we did not get a 'range' on R6, and the access
+                        * attempt will fail.
+                        */
+                       {16, "R6=pkt(id=1,off=0,r=0,umin_value=2,umax_value=9223372036854775806,var_off=(0x2; 0x7ffffffffffffffc))"},
+               }
+       },
 };
 
 static int probe_filter_length(const struct bpf_insn *fp)
@@ -470,10 +526,15 @@ static int do_test_single(struct bpf_align_test *test)
        fd_prog = bpf_verify_program(prog_type ? : BPF_PROG_TYPE_SOCKET_FILTER,
                                     prog, prog_len, 1, "GPL", 0,
                                     bpf_vlog, sizeof(bpf_vlog), 2);
-       if (fd_prog < 0) {
+       if (fd_prog < 0 && test->result != REJECT) {
                printf("Failed to load program.\n");
                printf("%s", bpf_vlog);
                ret = 1;
+       } else if (fd_prog >= 0 && test->result == REJECT) {
+               printf("Unexpected success to load!\n");
+               printf("%s", bpf_vlog);
+               ret = 1;
+               close(fd_prog);
        } else {
                ret = 0;
                /* We make a local copy so that we can strtok() it */
@@ -506,7 +567,8 @@ static int do_test_single(struct bpf_align_test *test)
                                break;
                        }
                }
-               close(fd_prog);
+               if (fd_prog >= 0)
+                       close(fd_prog);
        }
        return ret;
 }