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bpf: permits narrower load from bpf program context fields

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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 <daniel@iogearbox.net>
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Yonghong Song
2017-06-13 15:52:13 -07:00
committed by David S. Miller
parent a88e2676a6
commit 31fd85816d
6 changed files with 124 additions and 119 deletions
Download Patch File Download Diff File Expand all files Collapse all files

92
tools/testing/selftests/bpf/test_verifier.c
View File

@ -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",