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authorYonghong Song <yhs@fb.com>2017-06-13 15:52:13 -0700
committerDavid S. Miller <davem@davemloft.net>2017-06-14 14:56:25 -0400
commit31fd85816dbe3a714bcc3f67c17c3dd87011f79e (patch)
treed8c694e4997605254ea96a76c5d633f60ee091cf /kernel/trace
parenta88e2676a6cd3352c2f590f872233d83d8db289c (diff)
downloadop-kernel-dev-31fd85816dbe3a714bcc3f67c17c3dd87011f79e.zip
op-kernel-dev-31fd85816dbe3a714bcc3f67c17c3dd87011f79e.tar.gz
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 <daniel@iogearbox.net> Signed-off-by: Yonghong Song <yhs@fb.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel/trace')
-rw-r--r--kernel/trace/bpf_trace.c21
1 files changed, 15 insertions, 6 deletions
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 051d7fc..9d3ec82 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -479,7 +479,7 @@ static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func
/* bpf+kprobe programs can access fields of 'struct pt_regs' */
static bool kprobe_prog_is_valid_access(int off, int size, enum bpf_access_type type,
- enum bpf_reg_type *reg_type)
+ enum bpf_reg_type *reg_type, int *ctx_field_size)
{
if (off < 0 || off >= sizeof(struct pt_regs))
return false;
@@ -562,7 +562,7 @@ static const struct bpf_func_proto *tp_prog_func_proto(enum bpf_func_id func_id)
}
static bool tp_prog_is_valid_access(int off, int size, enum bpf_access_type type,
- enum bpf_reg_type *reg_type)
+ enum bpf_reg_type *reg_type, int *ctx_field_size)
{
if (off < sizeof(void *) || off >= PERF_MAX_TRACE_SIZE)
return false;
@@ -581,17 +581,26 @@ const struct bpf_verifier_ops tracepoint_prog_ops = {
};
static bool pe_prog_is_valid_access(int off, int size, enum bpf_access_type type,
- enum bpf_reg_type *reg_type)
+ enum bpf_reg_type *reg_type, int *ctx_field_size)
{
+ int sample_period_off;
+
if (off < 0 || off >= sizeof(struct bpf_perf_event_data))
return false;
if (type != BPF_READ)
return false;
if (off % size != 0)
return false;
- if (off == offsetof(struct bpf_perf_event_data, sample_period)) {
- if (size != sizeof(u64))
- return false;
+
+ /* permit 1, 2, 4 byte narrower and 8 normal read access to sample_period */
+ sample_period_off = offsetof(struct bpf_perf_event_data, sample_period);
+ if (off >= sample_period_off && off < sample_period_off + sizeof(__u64)) {
+ *ctx_field_size = 8;
+#ifdef __LITTLE_ENDIAN
+ return (off & 0x7) == 0 && size <= 8 && (size & (size - 1)) == 0;
+#else
+ return ((off & 0x7) + size) == 8 && size <= 8 && (size & (size - 1)) == 0;
+#endif
} else {
if (size != sizeof(long))
return false;
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