[ Upstream commit 64870feebecb ]
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@gmail.com Link: https://lore.kernel.org/r/20231024000917.12153-7-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov ast@kernel.org --- 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 764a68420c3e..c20c4e38b71c 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)