From cb578c1c9cf60275f258b5af7929c2a54a188f66 Mon Sep 17 00:00:00 2001 From: Eduard Zingerman Date: Fri, 9 Dec 2022 15:57:28 +0200 Subject: [PATCH] selftests/bpf: test cases for regsafe() bug skipping check_id() Under certain conditions it was possible for verifier.c:regsafe() to skip check_id() call. This commit adds negative test cases previously errorneously accepted as safe. Signed-off-by: Eduard Zingerman Link: https://lore.kernel.org/r/20221209135733.28851-3-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov --- .../bpf/verifier/direct_packet_access.c | 54 +++++++++++++++++++ .../selftests/bpf/verifier/value_or_null.c | 49 +++++++++++++++++ 2 files changed, 103 insertions(+) diff --git a/tools/testing/selftests/bpf/verifier/direct_packet_access.c b/tools/testing/selftests/bpf/verifier/direct_packet_access.c index 11acd1855acf..dce2e28aeb43 100644 --- a/tools/testing/selftests/bpf/verifier/direct_packet_access.c +++ b/tools/testing/selftests/bpf/verifier/direct_packet_access.c @@ -654,3 +654,57 @@ .result = ACCEPT, .prog_type = BPF_PROG_TYPE_SCHED_CLS, }, +{ + "direct packet access: test30 (check_id() in regsafe(), bad access)", + .insns = { + /* r9 = ctx */ + BPF_MOV64_REG(BPF_REG_9, BPF_REG_1), + /* r7 = ktime_get_ns() */ + BPF_EMIT_CALL(BPF_FUNC_ktime_get_ns), + BPF_MOV64_REG(BPF_REG_7, BPF_REG_0), + /* r6 = ktime_get_ns() */ + BPF_EMIT_CALL(BPF_FUNC_ktime_get_ns), + BPF_MOV64_REG(BPF_REG_6, BPF_REG_0), + /* r2 = ctx->data + * r3 = ctx->data + * r4 = ctx->data_end + */ + BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_9, offsetof(struct __sk_buff, data)), + BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_9, offsetof(struct __sk_buff, data)), + BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_9, offsetof(struct __sk_buff, data_end)), + /* if r6 > 100 goto exit + * if r7 > 100 goto exit + */ + BPF_JMP_IMM(BPF_JGT, BPF_REG_6, 100, 9), + BPF_JMP_IMM(BPF_JGT, BPF_REG_7, 100, 8), + /* r2 += r6 ; this forces assignment of ID to r2 + * r2 += 1 ; get some fixed off for r2 + * r3 += r7 ; this forces assignment of ID to r3 + * r3 += 1 ; get some fixed off for r3 + */ + BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_6), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, 1), + BPF_ALU64_REG(BPF_ADD, BPF_REG_3, BPF_REG_7), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, 1), + /* if r6 > r7 goto +1 ; no new information about the state is derived from + * ; this check, thus produced verifier states differ + * ; only in 'insn_idx' + * r2 = r3 ; optionally share ID between r2 and r3 + */ + BPF_JMP_REG(BPF_JNE, BPF_REG_6, BPF_REG_7, 1), + BPF_MOV64_REG(BPF_REG_2, BPF_REG_3), + /* if r3 > ctx->data_end goto exit */ + BPF_JMP_REG(BPF_JGT, BPF_REG_3, BPF_REG_4, 1), + /* r5 = *(u8 *) (r2 - 1) ; access packet memory using r2, + * ; this is not always safe + */ + BPF_LDX_MEM(BPF_B, BPF_REG_5, BPF_REG_2, -1), + /* exit(0) */ + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .flags = BPF_F_TEST_STATE_FREQ, + .result = REJECT, + .errstr = "invalid access to packet, off=0 size=1, R2", + .prog_type = BPF_PROG_TYPE_SCHED_CLS, +}, diff --git a/tools/testing/selftests/bpf/verifier/value_or_null.c b/tools/testing/selftests/bpf/verifier/value_or_null.c index 3ecb70a3d939..52a8bca14f03 100644 --- a/tools/testing/selftests/bpf/verifier/value_or_null.c +++ b/tools/testing/selftests/bpf/verifier/value_or_null.c @@ -169,3 +169,52 @@ .prog_type = BPF_PROG_TYPE_SCHED_CLS, .result = ACCEPT, }, +{ + "MAP_VALUE_OR_NULL check_ids() in regsafe()", + .insns = { + BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0), + /* r9 = map_lookup_elem(...) */ + BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), + BPF_LD_MAP_FD(BPF_REG_1, + 0), + BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem), + BPF_MOV64_REG(BPF_REG_9, BPF_REG_0), + /* r8 = map_lookup_elem(...) */ + BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), + BPF_LD_MAP_FD(BPF_REG_1, + 0), + BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem), + BPF_MOV64_REG(BPF_REG_8, BPF_REG_0), + /* r7 = ktime_get_ns() */ + BPF_EMIT_CALL(BPF_FUNC_ktime_get_ns), + BPF_MOV64_REG(BPF_REG_7, BPF_REG_0), + /* r6 = ktime_get_ns() */ + BPF_EMIT_CALL(BPF_FUNC_ktime_get_ns), + BPF_MOV64_REG(BPF_REG_6, BPF_REG_0), + /* if r6 > r7 goto +1 ; no new information about the state is derived from + * ; this check, thus produced verifier states differ + * ; only in 'insn_idx' + * r9 = r8 ; optionally share ID between r9 and r8 + */ + BPF_JMP_REG(BPF_JGT, BPF_REG_6, BPF_REG_7, 1), + BPF_MOV64_REG(BPF_REG_9, BPF_REG_8), + /* if r9 == 0 goto */ + BPF_JMP_IMM(BPF_JEQ, BPF_REG_9, 0, 1), + /* read map value via r8, this is not always + * safe because r8 might be not equal to r9. + */ + BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_8, 0), + /* exit 0 */ + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .flags = BPF_F_TEST_STATE_FREQ, + .fixup_map_hash_8b = { 3, 9 }, + .result = REJECT, + .errstr = "R8 invalid mem access 'map_value_or_null'", + .result_unpriv = REJECT, + .errstr_unpriv = "", + .prog_type = BPF_PROG_TYPE_CGROUP_SKB, +},