From 31fd85816dbe3a714bcc3f67c17c3dd87011f79e Mon Sep 17 00:00:00 2001 From: Yonghong Song Date: Tue, 13 Jun 2017 15:52:13 -0700 Subject: bpf: permits narrower load from bpf program context fields Currently, verifier will reject a program if it contains an narrower load from the bpf context structure. For example, __u8 h = __sk_buff->hash, or __u16 p = __sk_buff->protocol __u32 sample_period = bpf_perf_event_data->sample_period which are narrower loads of 4-byte or 8-byte field. This patch solves the issue by: . Introduce a new parameter ctx_field_size to carry the field size of narrower load from prog type specific *__is_valid_access validator back to verifier. . The non-zero ctx_field_size for a memory access indicates (1). underlying prog type specific convert_ctx_accesses supporting non-whole-field access (2). the current insn is a narrower or whole field access. . In verifier, for such loads where load memory size is less than ctx_field_size, verifier transforms it to a full field load followed by proper masking. . Currently, __sk_buff and bpf_perf_event_data->sample_period are supporting narrowing loads. . Narrower stores are still not allowed as typical ctx stores are just normal stores. Because of this change, some tests in verifier will fail and these tests are removed. As a bonus, rename some out of bound __sk_buff->cb access to proper field name and remove two redundant "skb cb oob" tests. Acked-by: Daniel Borkmann Signed-off-by: Yonghong Song Signed-off-by: David S. Miller --- tools/testing/selftests/bpf/test_verifier.c | 92 ++++------------------------- 1 file changed, 13 insertions(+), 79 deletions(-) (limited to 'tools/testing') diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c index 4ee4708b0d60..13341700930c 100644 --- a/tools/testing/selftests/bpf/test_verifier.c +++ b/tools/testing/selftests/bpf/test_verifier.c @@ -1073,44 +1073,22 @@ static struct bpf_test tests[] = { .result = ACCEPT, }, { - "check cb access: byte, oob 1", + "__sk_buff->hash, offset 0, byte store not permitted", .insns = { BPF_MOV64_IMM(BPF_REG_0, 0), BPF_STX_MEM(BPF_B, BPF_REG_1, BPF_REG_0, - offsetof(struct __sk_buff, cb[4]) + 4), + offsetof(struct __sk_buff, hash)), BPF_EXIT_INSN(), }, .errstr = "invalid bpf_context access", .result = REJECT, }, { - "check cb access: byte, oob 2", + "__sk_buff->tc_index, offset 3, byte store not permitted", .insns = { BPF_MOV64_IMM(BPF_REG_0, 0), BPF_STX_MEM(BPF_B, BPF_REG_1, BPF_REG_0, - offsetof(struct __sk_buff, cb[0]) - 1), - BPF_EXIT_INSN(), - }, - .errstr = "invalid bpf_context access", - .result = REJECT, - }, - { - "check cb access: byte, oob 3", - .insns = { - BPF_MOV64_IMM(BPF_REG_0, 0), - BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_1, - offsetof(struct __sk_buff, cb[4]) + 4), - BPF_EXIT_INSN(), - }, - .errstr = "invalid bpf_context access", - .result = REJECT, - }, - { - "check cb access: byte, oob 4", - .insns = { - BPF_MOV64_IMM(BPF_REG_0, 0), - BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_1, - offsetof(struct __sk_buff, cb[0]) - 1), + offsetof(struct __sk_buff, tc_index) + 3), BPF_EXIT_INSN(), }, .errstr = "invalid bpf_context access", @@ -1188,44 +1166,22 @@ static struct bpf_test tests[] = { .result = REJECT, }, { - "check cb access: half, oob 1", + "check __sk_buff->hash, offset 0, half store not permitted", .insns = { BPF_MOV64_IMM(BPF_REG_0, 0), BPF_STX_MEM(BPF_H, BPF_REG_1, BPF_REG_0, - offsetof(struct __sk_buff, cb[4]) + 4), + offsetof(struct __sk_buff, hash)), BPF_EXIT_INSN(), }, .errstr = "invalid bpf_context access", .result = REJECT, }, { - "check cb access: half, oob 2", + "check __sk_buff->tc_index, offset 2, half store not permitted", .insns = { BPF_MOV64_IMM(BPF_REG_0, 0), BPF_STX_MEM(BPF_H, BPF_REG_1, BPF_REG_0, - offsetof(struct __sk_buff, cb[0]) - 2), - BPF_EXIT_INSN(), - }, - .errstr = "invalid bpf_context access", - .result = REJECT, - }, - { - "check cb access: half, oob 3", - .insns = { - BPF_MOV64_IMM(BPF_REG_0, 0), - BPF_LDX_MEM(BPF_H, BPF_REG_0, BPF_REG_1, - offsetof(struct __sk_buff, cb[4]) + 4), - BPF_EXIT_INSN(), - }, - .errstr = "invalid bpf_context access", - .result = REJECT, - }, - { - "check cb access: half, oob 4", - .insns = { - BPF_MOV64_IMM(BPF_REG_0, 0), - BPF_LDX_MEM(BPF_H, BPF_REG_0, BPF_REG_1, - offsetof(struct __sk_buff, cb[0]) - 2), + offsetof(struct __sk_buff, tc_index) + 2), BPF_EXIT_INSN(), }, .errstr = "invalid bpf_context access", @@ -1366,28 +1322,6 @@ static struct bpf_test tests[] = { }, { "check cb access: double, oob 2", - .insns = { - BPF_MOV64_IMM(BPF_REG_0, 0), - BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_0, - offsetof(struct __sk_buff, cb[4]) + 8), - BPF_EXIT_INSN(), - }, - .errstr = "invalid bpf_context access", - .result = REJECT, - }, - { - "check cb access: double, oob 3", - .insns = { - BPF_MOV64_IMM(BPF_REG_0, 0), - BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_0, - offsetof(struct __sk_buff, cb[0]) - 8), - BPF_EXIT_INSN(), - }, - .errstr = "invalid bpf_context access", - .result = REJECT, - }, - { - "check cb access: double, oob 4", .insns = { BPF_MOV64_IMM(BPF_REG_0, 0), BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, @@ -1398,22 +1332,22 @@ static struct bpf_test tests[] = { .result = REJECT, }, { - "check cb access: double, oob 5", + "check __sk_buff->ifindex dw store not permitted", .insns = { BPF_MOV64_IMM(BPF_REG_0, 0), - BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, - offsetof(struct __sk_buff, cb[4]) + 8), + BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_0, + offsetof(struct __sk_buff, ifindex)), BPF_EXIT_INSN(), }, .errstr = "invalid bpf_context access", .result = REJECT, }, { - "check cb access: double, oob 6", + "check __sk_buff->ifindex dw load not permitted", .insns = { BPF_MOV64_IMM(BPF_REG_0, 0), BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, - offsetof(struct __sk_buff, cb[0]) - 8), + offsetof(struct __sk_buff, ifindex)), BPF_EXIT_INSN(), }, .errstr = "invalid bpf_context access", -- cgit v1.2.3