From: Eduard Zingerman Date: Wed, 11 Jun 2025 20:08:36 +0000 (-0700) Subject: selftests/bpf: tests with a loop state missing read/precision mark X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5159482fdb2b4c15cb0a087e41d8bc5d730bb697;p=thirdparty%2Fkernel%2Fstable.git selftests/bpf: tests with a loop state missing read/precision mark The test case absent_mark_in_the_middle_state is equivalent of the following C program: 1: r8 = bpf_get_prandom_u32(); 2: r6 = -32; 3: bpf_iter_num_new(&fp[-8], 0, 10); 4: if (unlikely(bpf_get_prandom_u32())) 5: r6 = -31; 6: for (;;) { 7: if (!bpf_iter_num_next(&fp[-8])) 8: break; 9: if (unlikely(bpf_get_prandom_u32())) 10: *(u64 *)(fp + r6) = 7; 11: } 12: bpf_iter_num_destroy(&fp[-8]); 13: return 0; W/o a fix that instructs verifier to ignore branches count for loop entries verification proceeds as follows: - 1-4, state is {r6=-32,fp-8=active}; - 6, checkpoint A is created with {r6=-32,fp-8=active}; - 7, checkpoint B is created with {r6=-32,fp-8=active}, push state {r6=-32,fp-8=active} from 7 to 9; - 8,12,13, {r6=-32,fp-8=drained}, exit; - pop state with {r6=-32,fp-8=active} from 7 to 9; - 9, push state {r6=-32,fp-8=active} from 9 to 10; - 6, checkpoint C is created with {r6=-32,fp-8=active}; - 7, checkpoint A is hit, no precision propagated for r6 to C; - pop state {r6=-32,fp-8=active} from 9 to 10; - 10, state is {r6=-31,fp-8=active}, r6 is marked as read and precise, these marks are propagated to checkpoints A and B (but not C, as it is not the parent of current state; - 6, {r6=-31,fp-8=active} checkpoint C is hit, because r6 is not marked precise for this checkpoint; - the program is accepted, despite a possibility of unaligned u64 stack access at offset -31. The test case absent_mark_in_the_middle_state2 is similar except the following change: r8 = bpf_get_prandom_u32(); r6 = -32; bpf_iter_num_new(&fp[-8], 0, 10); if (unlikely(bpf_get_prandom_u32())) { r6 = -31; + jump_into_loop: + goto +0; + goto loop; + } + if (unlikely(bpf_get_prandom_u32())) + goto jump_into_loop; + loop: for (;;) { if (!bpf_iter_num_next(&fp[-8])) break; if (unlikely(bpf_get_prandom_u32())) *(u64 *)(fp + r6) = 7; } bpf_iter_num_destroy(&fp[-8]) return 0 The goal is to check that read/precision marks are propagated to checkpoint created at 'goto +0' that resides outside of the loop. The test case absent_mark_in_the_middle_state3 is a bit different and is equivalent to the C program below: int absent_mark_in_the_middle_state3(void) { bpf_iter_num_new(&fp[-8], 0, 10) loop1(-32, &fp[-8]) loop1_wrapper(&fp[-8]) bpf_iter_num_destroy(&fp[-8]) } int loop1(num, iter) { while (bpf_iter_num_next(iter)) { if (unlikely(bpf_get_prandom_u32())) *(fp + num) = 7; } return 0 } int loop1_wrapper(iter) { r6 = -32; if (unlikely(bpf_get_prandom_u32())) r6 = -31; loop1(r6, iter); return 0; } The unsafe state is reached in a similar manner, but the loop is located inside a subprogram that is called from two locations in the main subprogram. This detail is important for exercising bpf_scc_visit->backedges memory management. Signed-off-by: Eduard Zingerman Link: https://lore.kernel.org/r/20250611200836.4135542-11-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov --- diff --git a/tools/testing/selftests/bpf/progs/iters.c b/tools/testing/selftests/bpf/progs/iters.c index 76adf4a8f2da..7dd92a303bf6 100644 --- a/tools/testing/selftests/bpf/progs/iters.c +++ b/tools/testing/selftests/bpf/progs/iters.c @@ -1649,4 +1649,281 @@ int clean_live_states(const void *ctx) return 0; } +SEC("?raw_tp") +__flag(BPF_F_TEST_STATE_FREQ) +__failure __msg("misaligned stack access off 0+-31+0 size 8") +__naked int absent_mark_in_the_middle_state(void) +{ + /* This is equivalent to C program below. + * + * r8 = bpf_get_prandom_u32(); + * r6 = -32; + * bpf_iter_num_new(&fp[-8], 0, 10); + * if (unlikely(bpf_get_prandom_u32())) + * r6 = -31; + * while (bpf_iter_num_next(&fp[-8])) { + * if (unlikely(bpf_get_prandom_u32())) + * *(fp + r6) = 7; + * } + * bpf_iter_num_destroy(&fp[-8]) + * return 0 + */ + asm volatile ( + "call %[bpf_get_prandom_u32];" + "r8 = r0;" + "r7 = 0;" + "r6 = -32;" + "r0 = 0;" + "*(u64 *)(r10 - 16) = r0;" + "r1 = r10;" + "r1 += -8;" + "r2 = 0;" + "r3 = 10;" + "call %[bpf_iter_num_new];" + "call %[bpf_get_prandom_u32];" + "if r0 == r8 goto change_r6_%=;" + "loop_%=:" + "call noop;" + "r1 = r10;" + "r1 += -8;" + "call %[bpf_iter_num_next];" + "if r0 == 0 goto loop_end_%=;" + "call %[bpf_get_prandom_u32];" + "if r0 == r8 goto use_r6_%=;" + "goto loop_%=;" + "loop_end_%=:" + "r1 = r10;" + "r1 += -8;" + "call %[bpf_iter_num_destroy];" + "r0 = 0;" + "exit;" + "use_r6_%=:" + "r0 = r10;" + "r0 += r6;" + "r1 = 7;" + "*(u64 *)(r0 + 0) = r1;" + "goto loop_%=;" + "change_r6_%=:" + "r6 = -31;" + "goto loop_%=;" + : + : __imm(bpf_iter_num_new), + __imm(bpf_iter_num_next), + __imm(bpf_iter_num_destroy), + __imm(bpf_get_prandom_u32) + : __clobber_all + ); +} + +__used __naked +static int noop(void) +{ + asm volatile ( + "r0 = 0;" + "exit;" + ); +} + +SEC("?raw_tp") +__flag(BPF_F_TEST_STATE_FREQ) +__failure __msg("misaligned stack access off 0+-31+0 size 8") +__naked int absent_mark_in_the_middle_state2(void) +{ + /* This is equivalent to C program below. + * + * r8 = bpf_get_prandom_u32(); + * r6 = -32; + * bpf_iter_num_new(&fp[-8], 0, 10); + * if (unlikely(bpf_get_prandom_u32())) { + * r6 = -31; + * jump_into_loop: + * goto +0; + * goto loop; + * } + * if (unlikely(bpf_get_prandom_u32())) + * goto jump_into_loop; + * loop: + * while (bpf_iter_num_next(&fp[-8])) { + * if (unlikely(bpf_get_prandom_u32())) + * *(fp + r6) = 7; + * } + * bpf_iter_num_destroy(&fp[-8]) + * return 0 + */ + asm volatile ( + "call %[bpf_get_prandom_u32];" + "r8 = r0;" + "r7 = 0;" + "r6 = -32;" + "r0 = 0;" + "*(u64 *)(r10 - 16) = r0;" + "r1 = r10;" + "r1 += -8;" + "r2 = 0;" + "r3 = 10;" + "call %[bpf_iter_num_new];" + "call %[bpf_get_prandom_u32];" + "if r0 == r8 goto change_r6_%=;" + "call %[bpf_get_prandom_u32];" + "if r0 == r8 goto jump_into_loop_%=;" + "loop_%=:" + "r1 = r10;" + "r1 += -8;" + "call %[bpf_iter_num_next];" + "if r0 == 0 goto loop_end_%=;" + "call %[bpf_get_prandom_u32];" + "if r0 == r8 goto use_r6_%=;" + "goto loop_%=;" + "loop_end_%=:" + "r1 = r10;" + "r1 += -8;" + "call %[bpf_iter_num_destroy];" + "r0 = 0;" + "exit;" + "use_r6_%=:" + "r0 = r10;" + "r0 += r6;" + "r1 = 7;" + "*(u64 *)(r0 + 0) = r1;" + "goto loop_%=;" + "change_r6_%=:" + "r6 = -31;" + "jump_into_loop_%=: " + "goto +0;" + "goto loop_%=;" + : + : __imm(bpf_iter_num_new), + __imm(bpf_iter_num_next), + __imm(bpf_iter_num_destroy), + __imm(bpf_get_prandom_u32) + : __clobber_all + ); +} + +SEC("?raw_tp") +__flag(BPF_F_TEST_STATE_FREQ) +__failure __msg("misaligned stack access off 0+-31+0 size 8") +__naked int absent_mark_in_the_middle_state3(void) +{ + /* + * bpf_iter_num_new(&fp[-8], 0, 10) + * loop1(-32, &fp[-8]) + * loop1_wrapper(&fp[-8]) + * bpf_iter_num_destroy(&fp[-8]) + */ + asm volatile ( + "r1 = r10;" + "r1 += -8;" + "r2 = 0;" + "r3 = 10;" + "call %[bpf_iter_num_new];" + /* call #1 */ + "r1 = -32;" + "r2 = r10;" + "r2 += -8;" + "call loop1;" + "r1 = r10;" + "r1 += -8;" + "call %[bpf_iter_num_destroy];" + /* call #2 */ + "r1 = r10;" + "r1 += -8;" + "r2 = 0;" + "r3 = 10;" + "call %[bpf_iter_num_new];" + "r1 = r10;" + "r1 += -8;" + "call loop1_wrapper;" + /* return */ + "r1 = r10;" + "r1 += -8;" + "call %[bpf_iter_num_destroy];" + "r0 = 0;" + "exit;" + : + : __imm(bpf_iter_num_new), + __imm(bpf_iter_num_destroy), + __imm(bpf_get_prandom_u32) + : __clobber_all + ); +} + +__used __naked +static int loop1(void) +{ + /* + * int loop1(num, iter) { + * r6 = num; + * r7 = iter; + * while (bpf_iter_num_next(r7)) { + * if (unlikely(bpf_get_prandom_u32())) + * *(fp + r6) = 7; + * } + * return 0 + * } + */ + asm volatile ( + "r6 = r1;" + "r7 = r2;" + "call %[bpf_get_prandom_u32];" + "r8 = r0;" + "loop_%=:" + "r1 = r7;" + "call %[bpf_iter_num_next];" + "if r0 == 0 goto loop_end_%=;" + "call %[bpf_get_prandom_u32];" + "if r0 == r8 goto use_r6_%=;" + "goto loop_%=;" + "loop_end_%=:" + "r0 = 0;" + "exit;" + "use_r6_%=:" + "r0 = r10;" + "r0 += r6;" + "r1 = 7;" + "*(u64 *)(r0 + 0) = r1;" + "goto loop_%=;" + : + : __imm(bpf_iter_num_next), + __imm(bpf_get_prandom_u32) + : __clobber_all + ); +} + +__used __naked +static int loop1_wrapper(void) +{ + /* + * int loop1_wrapper(iter) { + * r6 = -32; + * r7 = iter; + * if (unlikely(bpf_get_prandom_u32())) + * r6 = -31; + * loop1(r6, r7); + * return 0; + * } + */ + asm volatile ( + "r6 = -32;" + "r7 = r1;" + "call %[bpf_get_prandom_u32];" + "r8 = r0;" + "call %[bpf_get_prandom_u32];" + "if r0 == r8 goto change_r6_%=;" + "loop_%=:" + "r1 = r6;" + "r2 = r7;" + "call loop1;" + "r0 = 0;" + "exit;" + "change_r6_%=:" + "r6 = -31;" + "goto loop_%=;" + : + : __imm(bpf_iter_num_next), + __imm(bpf_get_prandom_u32) + : __clobber_all + ); +} + char _license[] SEC("license") = "GPL";