A convoluted test case for iterators convergence logic that
demonstrates that states with branch count equal to 0 might still be
a part of not completely explored loop.
E.g. consider the following state diagram:
initial Here state 'succ' was processed first,
| it was eventually tracked to produce a
V state identical to 'hdr'.
.---------> hdr All branches from 'succ' had been explored
| | and thus 'succ' has its .branches == 0.
| V
| .------... Suppose states 'cur' and 'succ' correspond
| | | to the same instruction + callsites.
| V V In such case it is necessary to check
| ... ... whether 'succ' and 'cur' are identical.
| | | If 'succ' and 'cur' are a part of the same loop
| V V they have to be compared exactly.
| succ <- cur
| |
| V
| ...
| |
'----'
Signed-off-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
---
tools/testing/selftests/bpf/progs/iters.c | 177 ++++++++++++++++++++++
1 file changed, 177 insertions(+)
diff --git a/tools/testing/selftests/bpf/progs/iters.c b/tools/testing/selftests/bpf/progs/iters.c
index ee85cc6d3444..89aaddec9a6d 100644
--- a/tools/testing/selftests/bpf/progs/iters.c
+++ b/tools/testing/selftests/bpf/progs/iters.c
@@ -998,6 +998,183 @@ __naked int loop_state_deps1(void)
);
}
+SEC("?raw_tp")
+__failure
+__msg("math between fp pointer and register with unbounded")
+__flag(BPF_F_TEST_STATE_FREQ)
+__naked int loop_state_deps2(void)
+{
+ /* This is equivalent to C program below.
+ *
+ * The case turns out to be tricky in a sense that:
+ * - states with read+precise mark on c are explored only on a second
+ * iteration of the first inner loop and in a state which is pushed to
+ * states stack first.
+ * - states with c=-25 are explored only on a second iteration of the
+ * second inner loop and in a state which is pushed to states stack
+ * first.
+ *
+ * Depending on the details of iterator convergence logic
+ * verifier might stop states traversal too early and miss
+ * unsafe c=-25 memory access.
+ *
+ * j = iter_new(); // fp[-16]
+ * a = 0; // r6
+ * b = 0; // r7
+ * c = -24; // r8
+ * while (iter_next(j)) {
+ * i = iter_new(); // fp[-8]
+ * a = 0; // r6
+ * b = 0; // r7
+ * while (iter_next(i)) {
+ * if (a == 1) {
+ * a = 0;
+ * b = 1;
+ * } else if (a == 0) {
+ * a = 1;
+ * if (random() == 42)
+ * continue;
+ * if (b == 1) {
+ * *(r10 + c) = 7; // this is not safe
+ * iter_destroy(i);
+ * iter_destroy(j);
+ * return;
+ * }
+ * }
+ * }
+ * iter_destroy(i);
+ * i = iter_new(); // fp[-8]
+ * a = 0; // r6
+ * b = 0; // r7
+ * while (iter_next(i)) {
+ * if (a == 1) {
+ * a = 0;
+ * b = 1;
+ * } else if (a == 0) {
+ * a = 1;
+ * if (random() == 42)
+ * continue;
+ * if (b == 1) {
+ * a = 0;
+ * c = -25;
+ * }
+ * }
+ * }
+ * iter_destroy(i);
+ * }
+ * iter_destroy(j);
+ * return;
+ */
+ asm volatile (
+ "r1 = r10;"
+ "r1 += -16;"
+ "r2 = 0;"
+ "r3 = 10;"
+ "call %[bpf_iter_num_new];"
+ "r6 = 0;"
+ "r7 = 0;"
+ "r8 = -24;"
+ "j_loop_%=:"
+ "r1 = r10;"
+ "r1 += -16;"
+ "call %[bpf_iter_num_next];"
+ "if r0 == 0 goto j_loop_end_%=;"
+
+ /* first inner loop */
+ "r1 = r10;"
+ "r1 += -8;"
+ "r2 = 0;"
+ "r3 = 10;"
+ "call %[bpf_iter_num_new];"
+ "r6 = 0;"
+ "r7 = 0;"
+ "i_loop_%=:"
+ "r1 = r10;"
+ "r1 += -8;"
+ "call %[bpf_iter_num_next];"
+ "if r0 == 0 goto i_loop_end_%=;"
+ "check_one_r6_%=:"
+ "if r6 != 1 goto check_zero_r6_%=;"
+ "r6 = 0;"
+ "r7 = 1;"
+ "goto i_loop_%=;"
+ "check_zero_r6_%=:"
+ "if r6 != 0 goto i_loop_%=;"
+ "r6 = 1;"
+ "call %[bpf_get_prandom_u32];"
+ "if r0 != 42 goto check_one_r7_%=;"
+ "goto i_loop_%=;"
+ "check_one_r7_%=:"
+ "if r7 != 1 goto i_loop_%=;"
+ "r0 = r10;"
+ "r0 += r8;"
+ "r1 = 7;"
+ "*(u64 *)(r0 + 0) = r1;"
+ "r1 = r10;"
+ "r1 += -8;"
+ "call %[bpf_iter_num_destroy];"
+ "r1 = r10;"
+ "r1 += -16;"
+ "call %[bpf_iter_num_destroy];"
+ "r0 = 0;"
+ "exit;"
+ "i_loop_end_%=:"
+ "r1 = r10;"
+ "r1 += -8;"
+ "call %[bpf_iter_num_destroy];"
+
+ /* second inner loop */
+ "r1 = r10;"
+ "r1 += -8;"
+ "r2 = 0;"
+ "r3 = 10;"
+ "call %[bpf_iter_num_new];"
+ "r6 = 0;"
+ "r7 = 0;"
+ "i2_loop_%=:"
+ "r1 = r10;"
+ "r1 += -8;"
+ "call %[bpf_iter_num_next];"
+ "if r0 == 0 goto i2_loop_end_%=;"
+ "check2_one_r6_%=:"
+ "if r6 != 1 goto check2_zero_r6_%=;"
+ "r6 = 0;"
+ "r7 = 1;"
+ "goto i2_loop_%=;"
+ "check2_zero_r6_%=:"
+ "if r6 != 0 goto i2_loop_%=;"
+ "r6 = 1;"
+ "call %[bpf_get_prandom_u32];"
+ "if r0 != 42 goto check2_one_r7_%=;"
+ "goto i2_loop_%=;"
+ "check2_one_r7_%=:"
+ "if r7 != 1 goto i2_loop_%=;"
+ "r6 = 0;"
+ "r8 = -25;"
+ "goto i2_loop_%=;"
+ "i2_loop_end_%=:"
+ "r1 = r10;"
+ "r1 += -8;"
+ "call %[bpf_iter_num_destroy];"
+
+ "r6 = 0;"
+ "r7 = 0;"
+ "goto j_loop_%=;"
+ "j_loop_end_%=:"
+ "r1 = r10;"
+ "r1 += -16;"
+ "call %[bpf_iter_num_destroy];"
+ "r0 = 0;"
+ "exit;"
+ :
+ : __imm(bpf_get_prandom_u32),
+ __imm(bpf_iter_num_new),
+ __imm(bpf_iter_num_next),
+ __imm(bpf_iter_num_destroy)
+ : __clobber_all
+ );
+}
+
SEC("?raw_tp")
__success
__naked int triple_continue(void)
--
2.42.0
