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Date: Mon, 13 Jul 2020 09:17:42 -0700
From: Yonghong Song <yhs@...com>
To: <bpf@...r.kernel.org>, <netdev@...r.kernel.org>
CC: Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>, <kernel-team@...com>,
Martin KaFai Lau <kafai@...com>
Subject: [PATCH bpf-next 03/13] bpf: support readonly buffer in verifier
Two new readonly buffer PTR_TO_RDONLY_BUF or
PTR_TO_RDONLY_BUF_OR_NULL register states
are introduced. These new register states will be used
by later bpf map element iterator.
New register states share some similarity to
PTR_TO_TP_BUFFER as it will calculate accessed buffer
size during verification time. The accessed buffer
size will be later compared to other metrics during
later attach/link_create time.
Two differences between PTR_TO_TP_BUFFER and
PTR_TO_RDONLY_BUF[_OR_NULL].
PTR_TO_TP_BUFFER is for write only
and PTR_TO_RDONLY_BUF[_OR_NULL] is for read only.
In addition, a rdonly_buf_seq_id is also added to the
register state since it is possible for the same program
there could be two PTR_TO_RDONLY_BUF[_OR_NULL] ctx arguments.
For example, for bpf later map element iterator,
both key and value may be PTR_TO_TP_BUFFER_OR_NULL.
Similar to reg_state PTR_TO_BTF_ID_OR_NULL in bpf
iterator programs, PTR_TO_RDONLY_BUF_OR_NULL reg_type and
its rdonly_buf_seq_id can be set at
prog->aux->bpf_ctx_arg_aux, and bpf verifier will
retrieve the values during btf_ctx_access().
Later bpf map element iterator implementation
will show how such information will be assigned
during target registeration time.
Signed-off-by: Yonghong Song <yhs@...com>
---
include/linux/bpf.h | 7 ++++
include/linux/bpf_verifier.h | 2 +
kernel/bpf/btf.c | 13 +++++++
kernel/bpf/verifier.c | 74 +++++++++++++++++++++++++++++++-----
4 files changed, 87 insertions(+), 9 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 97c6e2605978..8f708d51733b 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -352,6 +352,8 @@ enum bpf_reg_type {
PTR_TO_BTF_ID_OR_NULL, /* reg points to kernel struct or NULL */
PTR_TO_MEM, /* reg points to valid memory region */
PTR_TO_MEM_OR_NULL, /* reg points to valid memory region or NULL */
+ PTR_TO_RDONLY_BUF, /* reg points to a readonly buffer */
+ PTR_TO_RDONLY_BUF_OR_NULL, /* reg points to a readonly buffer or NULL */
};
/* The information passed from prog-specific *_is_valid_access
@@ -362,6 +364,7 @@ struct bpf_insn_access_aux {
union {
int ctx_field_size;
u32 btf_id;
+ u32 rdonly_buf_seq_id;
};
struct bpf_verifier_log *log; /* for verbose logs */
};
@@ -678,8 +681,11 @@ struct bpf_jit_poke_descriptor {
struct bpf_ctx_arg_aux {
u32 offset;
enum bpf_reg_type reg_type;
+ u32 rdonly_buf_seq_id;
};
+#define BPF_MAX_RDONLY_BUF 2
+
struct bpf_prog_aux {
atomic64_t refcnt;
u32 used_map_cnt;
@@ -693,6 +699,7 @@ struct bpf_prog_aux {
u32 attach_btf_id; /* in-kernel BTF type id to attach to */
u32 ctx_arg_info_size;
const struct bpf_ctx_arg_aux *ctx_arg_info;
+ u32 max_rdonly_access[BPF_MAX_RDONLY_BUF];
struct bpf_prog *linked_prog;
bool verifier_zext; /* Zero extensions has been inserted by verifier. */
bool offload_requested;
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 53c7bd568c5d..063e4ab2dd77 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -56,6 +56,8 @@ struct bpf_reg_state {
u32 mem_size; /* for PTR_TO_MEM | PTR_TO_MEM_OR_NULL */
+ u32 rdonly_buf_seq_id; /* for PTR_TO_RDONLY_BUF */
+
/* Max size from any of the above. */
unsigned long raw;
};
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 4c3007f428b1..895de2b21385 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3809,6 +3809,19 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type,
btf_kind_str[BTF_INFO_KIND(t->info)]);
return false;
}
+
+ /* check for PTR_TO_RDONLY_BUF_OR_NULL */
+ for (i = 0; i < prog->aux->ctx_arg_info_size; i++) {
+ const struct bpf_ctx_arg_aux *ctx_arg_info = &prog->aux->ctx_arg_info[i];
+
+ if (ctx_arg_info->offset == off &&
+ ctx_arg_info->reg_type == PTR_TO_RDONLY_BUF_OR_NULL) {
+ info->reg_type = ctx_arg_info->reg_type;
+ info->rdonly_buf_seq_id = ctx_arg_info->rdonly_buf_seq_id;
+ return true;
+ }
+ }
+
if (t->type == 0)
/* This is a pointer to void.
* It is the same as scalar from the verifier safety pov.
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index b608185e1ffd..87801afa26fc 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -410,7 +410,8 @@ static bool reg_type_may_be_null(enum bpf_reg_type type)
type == PTR_TO_SOCK_COMMON_OR_NULL ||
type == PTR_TO_TCP_SOCK_OR_NULL ||
type == PTR_TO_BTF_ID_OR_NULL ||
- type == PTR_TO_MEM_OR_NULL;
+ type == PTR_TO_MEM_OR_NULL ||
+ type == PTR_TO_RDONLY_BUF_OR_NULL;
}
static bool reg_may_point_to_spin_lock(const struct bpf_reg_state *reg)
@@ -504,6 +505,8 @@ static const char * const reg_type_str[] = {
[PTR_TO_BTF_ID_OR_NULL] = "ptr_or_null_",
[PTR_TO_MEM] = "mem",
[PTR_TO_MEM_OR_NULL] = "mem_or_null",
+ [PTR_TO_RDONLY_BUF] = "rdonly_buf",
+ [PTR_TO_RDONLY_BUF_OR_NULL] = "rdonly_buf_or_null",
};
static char slot_type_char[] = {
@@ -579,6 +582,9 @@ static void print_verifier_state(struct bpf_verifier_env *env,
verbose(env, ",ks=%d,vs=%d",
reg->map_ptr->key_size,
reg->map_ptr->value_size);
+ else if (t == PTR_TO_RDONLY_BUF ||
+ t == PTR_TO_RDONLY_BUF_OR_NULL)
+ verbose(env, ",seq_id=%u", reg->rdonly_buf_seq_id);
if (tnum_is_const(reg->var_off)) {
/* Typically an immediate SCALAR_VALUE, but
* could be a pointer whose offset is too big
@@ -2174,6 +2180,8 @@ static bool is_spillable_regtype(enum bpf_reg_type type)
case PTR_TO_XDP_SOCK:
case PTR_TO_BTF_ID:
case PTR_TO_BTF_ID_OR_NULL:
+ case PTR_TO_RDONLY_BUF:
+ case PTR_TO_RDONLY_BUF_OR_NULL:
return true;
default:
return false;
@@ -2699,7 +2707,7 @@ static int check_packet_access(struct bpf_verifier_env *env, u32 regno, int off,
/* check access to 'struct bpf_context' fields. Supports fixed offsets only */
static int check_ctx_access(struct bpf_verifier_env *env, int insn_idx, int off, int size,
enum bpf_access_type t, enum bpf_reg_type *reg_type,
- u32 *btf_id)
+ u32 *btf_id, u32 *rdonly_buf_seq_id)
{
struct bpf_insn_access_aux info = {
.reg_type = *reg_type,
@@ -2719,6 +2727,8 @@ static int check_ctx_access(struct bpf_verifier_env *env, int insn_idx, int off,
if (*reg_type == PTR_TO_BTF_ID || *reg_type == PTR_TO_BTF_ID_OR_NULL)
*btf_id = info.btf_id;
+ else if (*reg_type == PTR_TO_RDONLY_BUF_OR_NULL)
+ *rdonly_buf_seq_id = info.rdonly_buf_seq_id;
else
env->insn_aux_data[insn_idx].ctx_field_size = info.ctx_field_size;
/* remember the offset of last byte accessed in ctx */
@@ -3053,14 +3063,15 @@ int check_ctx_reg(struct bpf_verifier_env *env,
return 0;
}
-static int check_tp_buffer_access(struct bpf_verifier_env *env,
- const struct bpf_reg_state *reg,
- int regno, int off, int size)
+static int __check_buffer_access(struct bpf_verifier_env *env,
+ const char *buf_info,
+ const struct bpf_reg_state *reg,
+ int regno, int off, int size)
{
if (off < 0) {
verbose(env,
- "R%d invalid tracepoint buffer access: off=%d, size=%d",
- regno, off, size);
+ "R%d invalid %s buffer access: off=%d, size=%d",
+ regno, buf_info, off, size);
return -EACCES;
}
if (!tnum_is_const(reg->var_off) || reg->var_off.value) {
@@ -3072,12 +3083,43 @@ static int check_tp_buffer_access(struct bpf_verifier_env *env,
regno, off, tn_buf);
return -EACCES;
}
+
+ return 0;
+}
+
+static int check_tp_buffer_access(struct bpf_verifier_env *env,
+ const struct bpf_reg_state *reg,
+ int regno, int off, int size)
+{
+ int err;
+
+ err = __check_buffer_access(env, "tracepoint", reg, regno, off, size);
+ if (err)
+ return err;
+
if (off + size > env->prog->aux->max_tp_access)
env->prog->aux->max_tp_access = off + size;
return 0;
}
+static int check_rdonly_buf_access(struct bpf_verifier_env *env,
+ const struct bpf_reg_state *reg,
+ int regno, int off, int size)
+{
+ u32 seq_id = reg->rdonly_buf_seq_id;
+ int err;
+
+ err = __check_buffer_access(env, "readonly", reg, regno, off, size);
+ if (err)
+ return err;
+
+ if (off + size > env->prog->aux->max_rdonly_access[seq_id])
+ env->prog->aux->max_rdonly_access[seq_id] = off + size;
+
+ return 0;
+}
+
/* BPF architecture zero extends alu32 ops into 64-bit registesr */
static void zext_32_to_64(struct bpf_reg_state *reg)
{
@@ -3327,7 +3369,7 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
mark_reg_unknown(env, regs, value_regno);
} else if (reg->type == PTR_TO_CTX) {
enum bpf_reg_type reg_type = SCALAR_VALUE;
- u32 btf_id = 0;
+ u32 btf_id = 0, rdonly_buf_seq_id = 0;
if (t == BPF_WRITE && value_regno >= 0 &&
is_pointer_value(env, value_regno)) {
@@ -3339,7 +3381,8 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
if (err < 0)
return err;
- err = check_ctx_access(env, insn_idx, off, size, t, ®_type, &btf_id);
+ err = check_ctx_access(env, insn_idx, off, size, t, ®_type, &btf_id,
+ &rdonly_buf_seq_id);
if (err)
verbose_linfo(env, insn_idx, "; ");
if (!err && t == BPF_READ && value_regno >= 0) {
@@ -3363,6 +3406,8 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
if (reg_type == PTR_TO_BTF_ID ||
reg_type == PTR_TO_BTF_ID_OR_NULL)
regs[value_regno].btf_id = btf_id;
+ else if (reg_type == PTR_TO_RDONLY_BUF_OR_NULL)
+ regs[value_regno].rdonly_buf_seq_id = rdonly_buf_seq_id;
}
regs[value_regno].type = reg_type;
}
@@ -3428,6 +3473,15 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
} else if (reg->type == CONST_PTR_TO_MAP) {
err = check_ptr_to_map_access(env, regs, regno, off, size, t,
value_regno);
+ } else if (reg->type == PTR_TO_RDONLY_BUF) {
+ if (t == BPF_WRITE) {
+ verbose(env, "R%d cannot write into %s\n",
+ regno, reg_type_str[reg->type]);
+ return -EACCES;
+ }
+ err = check_rdonly_buf_access(env, reg, regno, off, size);
+ if (!err && value_regno >= 0)
+ mark_reg_unknown(env, regs, value_regno);
} else {
verbose(env, "R%d invalid mem access '%s'\n", regno,
reg_type_str[reg->type]);
@@ -6803,6 +6857,8 @@ static void mark_ptr_or_null_reg(struct bpf_func_state *state,
reg->type = PTR_TO_BTF_ID;
} else if (reg->type == PTR_TO_MEM_OR_NULL) {
reg->type = PTR_TO_MEM;
+ } else if (reg->type == PTR_TO_RDONLY_BUF_OR_NULL) {
+ reg->type = PTR_TO_RDONLY_BUF;
}
if (is_null) {
/* We don't need id and ref_obj_id from this point
--
2.24.1
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