Verify that the following example is rejected by verifier:
r9 = ... some pointer with range X ...
r6 = ... unbound scalar ID=a ...
r7 = ... unbound scalar ID=b ...
if (r6 > r7) goto +1
r7 = r6
if (r7 > X) goto exit
r9 += r6
*(u64 *)r9 = Y
Also add test cases to check that check_alu_op() for BPF_MOV instruction does
not allocate scalar ID if source register is a constant.
Signed-off-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
---
.../selftests/bpf/progs/verifier_scalar_ids.c | 184 ++++++++++++++++++
1 file changed, 184 insertions(+)
diff --git a/tools/testing/selftests/bpf/progs/verifier_scalar_ids.c b/tools/testing/selftests/bpf/progs/verifier_scalar_ids.c
index 0f1071847490..00d80ba525d7 100644
--- a/tools/testing/selftests/bpf/progs/verifier_scalar_ids.c
+++ b/tools/testing/selftests/bpf/progs/verifier_scalar_ids.c
@@ -321,4 +321,188 @@ __naked void precision_two_ids(void)
: __clobber_all);
}
+/* Verify that check_ids() is used by regsafe() for scalars.
+ *
+ * r9 = ... some pointer with range X ...
+ * r6 = ... unbound scalar ID=a ...
+ * r7 = ... unbound scalar ID=b ...
+ * if (r6 > r7) goto +1
+ * r6 = r7
+ * if (r6 > X) goto exit
+ * r9 += r7
+ * *(u8 *)r9 = Y
+ *
+ * The memory access is safe only if r7 is bounded,
+ * which is true for one branch and not true for another.
+ */
+SEC("socket")
+__failure __msg("register with unbounded min value")
+__flag(BPF_F_TEST_STATE_FREQ)
+__naked void check_ids_in_regsafe(void)
+{
+ asm volatile (
+ /* Bump allocated stack */
+ "r1 = 0;"
+ "*(u64*)(r10 - 8) = r1;"
+ /* r9 = pointer to stack */
+ "r9 = r10;"
+ "r9 += -8;"
+ /* r7 = ktime_get_ns() */
+ "call %[bpf_ktime_get_ns];"
+ "r7 = r0;"
+ /* r6 = ktime_get_ns() */
+ "call %[bpf_ktime_get_ns];"
+ "r6 = r0;"
+ /* if r6 > r7 is an unpredictable jump */
+ "if r6 > r7 goto l1_%=;"
+ "r7 = r6;"
+"l1_%=:"
+ /* if r6 > 4 exit(0) */
+ "if r7 > 4 goto l2_%=;"
+ /* Access memory at r9[r7] */
+ "r9 += r6;"
+ "r0 = *(u8*)(r9 + 0);"
+"l2_%=:"
+ "r0 = 0;"
+ "exit;"
+ :
+ : __imm(bpf_ktime_get_ns)
+ : __clobber_all);
+}
+
+/* Similar to check_ids_in_regsafe.
+ * The l0 could be reached in two states:
+ *
+ * (1) r6{.id=A}, r7{.id=A}, r8{.id=B}
+ * (2) r6{.id=B}, r7{.id=A}, r8{.id=B}
+ *
+ * Where (2) is not safe, as "r7 > 4" check won't propagate range for it.
+ * This example would be considered safe without changes to
+ * mark_chain_precision() to track scalar values with equal IDs.
+ */
+SEC("socket")
+__failure __msg("register with unbounded min value")
+__flag(BPF_F_TEST_STATE_FREQ)
+__naked void check_ids_in_regsafe_2(void)
+{
+ asm volatile (
+ /* Bump allocated stack */
+ "r1 = 0;"
+ "*(u64*)(r10 - 8) = r1;"
+ /* r9 = pointer to stack */
+ "r9 = r10;"
+ "r9 += -8;"
+ /* r8 = ktime_get_ns() */
+ "call %[bpf_ktime_get_ns];"
+ "r8 = r0;"
+ /* r7 = ktime_get_ns() */
+ "call %[bpf_ktime_get_ns];"
+ "r7 = r0;"
+ /* r6 = ktime_get_ns() */
+ "call %[bpf_ktime_get_ns];"
+ "r6 = r0;"
+ /* scratch .id from r0 */
+ "r0 = 0;"
+ /* if r6 > r7 is an unpredictable jump */
+ "if r6 > r7 goto l1_%=;"
+ /* tie r6 and r7 .id */
+ "r6 = r7;"
+"l0_%=:"
+ /* if r7 > 4 exit(0) */
+ "if r7 > 4 goto l2_%=;"
+ /* Access memory at r9[r7] */
+ "r9 += r6;"
+ "r0 = *(u8*)(r9 + 0);"
+"l2_%=:"
+ "r0 = 0;"
+ "exit;"
+"l1_%=:"
+ /* tie r6 and r8 .id */
+ "r6 = r8;"
+ "goto l0_%=;"
+ :
+ : __imm(bpf_ktime_get_ns)
+ : __clobber_all);
+}
+
+/* Check that scalar IDs *are not* generated on register to register
+ * assignments if source register is a constant.
+ *
+ * If such IDs *are* generated the 'l1' below would be reached in
+ * two states:
+ *
+ * (1) r1{.id=A}, r2{.id=A}
+ * (2) r1{.id=C}, r2{.id=C}
+ *
+ * Thus forcing 'if r1 == r2' verification twice.
+ */
+SEC("socket")
+__success __log_level(2)
+__msg("11: (1d) if r3 == r4 goto pc+0")
+__msg("frame 0: propagating r3,r4")
+__msg("11: safe")
+__flag(BPF_F_TEST_STATE_FREQ)
+__naked void no_scalar_id_for_const(void)
+{
+ asm volatile (
+ "call %[bpf_ktime_get_ns];"
+ /* unpredictable jump */
+ "if r0 > 7 goto l0_%=;"
+ /* possibly generate same scalar ids for r3 and r4 */
+ "r1 = 0;"
+ "r1 = r1;"
+ "r3 = r1;"
+ "r4 = r1;"
+ "goto l1_%=;"
+"l0_%=:"
+ /* possibly generate different scalar ids for r3 and r4 */
+ "r1 = 0;"
+ "r2 = 0;"
+ "r3 = r1;"
+ "r4 = r2;"
+"l1_%=:"
+ /* predictable jump, marks r3 and r4 precise */
+ "if r3 == r4 goto +0;"
+ "r0 = 0;"
+ "exit;"
+ :
+ : __imm(bpf_ktime_get_ns)
+ : __clobber_all);
+}
+
+/* Same as no_scalar_id_for_const() but for 32-bit values */
+SEC("socket")
+__success __log_level(2)
+__msg("11: (1e) if w3 == w4 goto pc+0")
+__msg("frame 0: propagating r3,r4")
+__msg("11: safe")
+__flag(BPF_F_TEST_STATE_FREQ)
+__naked void no_scalar_id_for_const32(void)
+{
+ asm volatile (
+ "call %[bpf_ktime_get_ns];"
+ /* unpredictable jump */
+ "if r0 > 7 goto l0_%=;"
+ /* possibly generate same scalar ids for r3 and r4 */
+ "w1 = 0;"
+ "w1 = w1;"
+ "w3 = w1;"
+ "w4 = w1;"
+ "goto l1_%=;"
+"l0_%=:"
+ /* possibly generate different scalar ids for r3 and r4 */
+ "w1 = 0;"
+ "w2 = 0;"
+ "w3 = w1;"
+ "w4 = w2;"
+"l1_%=:"
+ /* predictable jump, marks r1 and r2 precise */
+ "if w3 == w4 goto +0;"
+ "r0 = 0;"
+ "exit;"
+ :
+ : __imm(bpf_ktime_get_ns)
+ : __clobber_all);
+}
+
char _license[] SEC("license") = "GPL";
--
2.40.1
