[PATCH 5.15 06/33] bpf: Introduce MEM_RDONLY flag

Greg Kroah-Hartman
2022-04-29T10:46:24Z

From: Hao Luo <haoluo@google.com>

commit 20b2aff4bc15bda809f994761d5719827d66c0b4 upstream.

This patch introduce a flag MEM_RDONLY to tag a reg value
pointing to read-only memory. It makes the following changes:

1. PTR_TO_RDWR_BUF -> PTR_TO_BUF
2. PTR_TO_RDONLY_BUF -> PTR_TO_BUF | MEM_RDONLY

Signed-off-by: Hao Luo <haoluo@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211217003152.48334-6-haoluo@google.com
Cc: stable@vger.kernel.org # 5.15.x
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/linux/bpf.h | 8 ++--
kernel/bpf/btf.c | 3 -
kernel/bpf/map_iter.c | 4 +-
kernel/bpf/verifier.c | 84 +++++++++++++++++++++++++++-------------------
net/core/bpf_sk_storage.c | 2 -
net/core/sock_map.c | 2 -
6 files changed, 60 insertions(+), 43 deletions(-)

--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -307,7 +307,10 @@ enum bpf_type_flag {
/* PTR may be NULL. */
PTR_MAYBE_NULL = BIT(0 + BPF_BASE_TYPE_BITS),

- __BPF_TYPE_LAST_FLAG = PTR_MAYBE_NULL,
+ /* MEM is read-only. */
+ MEM_RDONLY = BIT(1 + BPF_BASE_TYPE_BITS),
+
+ __BPF_TYPE_LAST_FLAG = MEM_RDONLY,
};

/* Max number of base types. */
@@ -488,8 +491,7 @@ enum bpf_reg_type {
* an explicit null check is required for this struct.
*/
PTR_TO_MEM, /* reg points to valid memory region */
- PTR_TO_RDONLY_BUF, /* reg points to a readonly buffer */
- PTR_TO_RDWR_BUF, /* reg points to a read/write buffer */
+ PTR_TO_BUF, /* reg points to a read/write buffer */
PTR_TO_PERCPU_BTF_ID, /* reg points to a percpu kernel variable */
PTR_TO_FUNC, /* reg points to a bpf program function */
__BPF_REG_TYPE_MAX,
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -4804,8 +4804,7 @@ bool btf_ctx_access(int off, int size, e

type = base_type(ctx_arg_info->reg_type);
flag = type_flag(ctx_arg_info->reg_type);
- if (ctx_arg_info->offset == off &&
- (type == PTR_TO_RDWR_BUF || type == PTR_TO_RDONLY_BUF) &&
+ if (ctx_arg_info->offset == off && type == PTR_TO_BUF &&
(flag & PTR_MAYBE_NULL)) {
info->reg_type = ctx_arg_info->reg_type;
return true;
--- a/kernel/bpf/map_iter.c
+++ b/kernel/bpf/map_iter.c
@@ -174,9 +174,9 @@ static const struct bpf_iter_reg bpf_map
.ctx_arg_info_size = 2,
.ctx_arg_info = {
{ offsetof(struct bpf_iter__bpf_map_elem, key),
- PTR_TO_RDONLY_BUF | PTR_MAYBE_NULL },
+ PTR_TO_BUF | PTR_MAYBE_NULL | MEM_RDONLY },
{ offsetof(struct bpf_iter__bpf_map_elem, value),
- PTR_TO_RDWR_BUF | PTR_MAYBE_NULL },
+ PTR_TO_BUF | PTR_MAYBE_NULL },
},
};

--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -458,6 +458,11 @@ static bool reg_type_may_be_refcounted_o
base_type(type) == PTR_TO_MEM;
}

+static bool type_is_rdonly_mem(u32 type)
+{
+ return type & MEM_RDONLY;
+}
+
static bool arg_type_may_be_refcounted(enum bpf_arg_type type)
{
return type == ARG_PTR_TO_SOCK_COMMON;
@@ -533,7 +538,7 @@ static bool is_cmpxchg_insn(const struct
static const char *reg_type_str(struct bpf_verifier_env *env,
enum bpf_reg_type type)
{
- char postfix[16] = {0};
+ char postfix[16] = {0}, prefix[16] = {0};
static const char * const str[] = {
[NOT_INIT] = "?",
[SCALAR_VALUE] = "inv",
@@ -553,8 +558,7 @@ static const char *reg_type_str(struct b
[PTR_TO_BTF_ID] = "ptr_",
[PTR_TO_PERCPU_BTF_ID] = "percpu_ptr_",
[PTR_TO_MEM] = "mem",
- [PTR_TO_RDONLY_BUF] = "rdonly_buf",
- [PTR_TO_RDWR_BUF] = "rdwr_buf",
+ [PTR_TO_BUF] = "buf",
[PTR_TO_FUNC] = "func",
[PTR_TO_MAP_KEY] = "map_key",
};
@@ -567,8 +571,11 @@ static const char *reg_type_str(struct b
strncpy(postfix, "_or_null", 16);
}

- snprintf(env->type_str_buf, TYPE_STR_BUF_LEN, "%s%s",
- str[base_type(type)], postfix);
+ if (type & MEM_RDONLY)
+ strncpy(prefix, "rdonly_", 16);
+
+ snprintf(env->type_str_buf, TYPE_STR_BUF_LEN, "%s%s%s",
+ prefix, str[base_type(type)], postfix);
return env->type_str_buf;
}

@@ -2546,8 +2553,7 @@ static bool is_spillable_regtype(enum bp
case PTR_TO_TCP_SOCK:
case PTR_TO_XDP_SOCK:
case PTR_TO_BTF_ID:
- case PTR_TO_RDONLY_BUF:
- case PTR_TO_RDWR_BUF:
+ case PTR_TO_BUF:
case PTR_TO_PERCPU_BTF_ID:
case PTR_TO_MEM:
case PTR_TO_FUNC:
@@ -4275,22 +4281,28 @@ static int check_mem_access(struct bpf_v
} 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(env, reg->type));
- return -EACCES;
+ } else if (base_type(reg->type) == PTR_TO_BUF) {
+ bool rdonly_mem = type_is_rdonly_mem(reg->type);
+ const char *buf_info;
+ u32 *max_access;
+
+ if (rdonly_mem) {
+ if (t == BPF_WRITE) {
+ verbose(env, "R%d cannot write into %s\n",
+ regno, reg_type_str(env, reg->type));
+ return -EACCES;
+ }
+ buf_info = "rdonly";
+ max_access = &env->prog->aux->max_rdonly_access;
+ } else {
+ buf_info = "rdwr";
+ max_access = &env->prog->aux->max_rdwr_access;
}
+
err = check_buffer_access(env, reg, regno, off, size, false,
- "rdonly",
- &env->prog->aux->max_rdonly_access);
- if (!err && value_regno >= 0)
- mark_reg_unknown(env, regs, value_regno);
- } else if (reg->type == PTR_TO_RDWR_BUF) {
- err = check_buffer_access(env, reg, regno, off, size, false,
- "rdwr",
- &env->prog->aux->max_rdwr_access);
- if (!err && t == BPF_READ && value_regno >= 0)
+ buf_info, max_access);
+
+ if (!err && value_regno >= 0 && (rdonly_mem || t == BPF_READ))
mark_reg_unknown(env, regs, value_regno);
} else {
verbose(env, "R%d invalid mem access '%s'\n", regno,
@@ -4551,8 +4563,10 @@ static int check_helper_mem_access(struc
struct bpf_call_arg_meta *meta)
{
struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];
+ const char *buf_info;
+ u32 *max_access;

- switch (reg->type) {
+ switch (base_type(reg->type)) {
case PTR_TO_PACKET:
case PTR_TO_PACKET_META:
return check_packet_access(env, regno, reg->off, access_size,
@@ -4571,18 +4585,20 @@ static int check_helper_mem_access(struc
return check_mem_region_access(env, regno, reg->off,
access_size, reg->mem_size,
zero_size_allowed);
- case PTR_TO_RDONLY_BUF:
- if (meta && meta->raw_mode)
- return -EACCES;
- return check_buffer_access(env, reg, regno, reg->off,
- access_size, zero_size_allowed,
- "rdonly",
- &env->prog->aux->max_rdonly_access);
- case PTR_TO_RDWR_BUF:
+ case PTR_TO_BUF:
+ if (type_is_rdonly_mem(reg->type)) {
+ if (meta && meta->raw_mode)
+ return -EACCES;
+
+ buf_info = "rdonly";
+ max_access = &env->prog->aux->max_rdonly_access;
+ } else {
+ buf_info = "rdwr";
+ max_access = &env->prog->aux->max_rdwr_access;
+ }
return check_buffer_access(env, reg, regno, reg->off,
access_size, zero_size_allowed,
- "rdwr",
- &env->prog->aux->max_rdwr_access);
+ buf_info, max_access);
case PTR_TO_STACK:
return check_stack_range_initialized(
env,
@@ -4858,8 +4874,8 @@ static const struct bpf_reg_types mem_ty
PTR_TO_MAP_KEY,
PTR_TO_MAP_VALUE,
PTR_TO_MEM,
- PTR_TO_RDONLY_BUF,
- PTR_TO_RDWR_BUF,
+ PTR_TO_BUF,
+ PTR_TO_BUF | MEM_RDONLY,
},
};

--- a/net/core/bpf_sk_storage.c
+++ b/net/core/bpf_sk_storage.c
@@ -929,7 +929,7 @@ static struct bpf_iter_reg bpf_sk_storag
{ offsetof(struct bpf_iter__bpf_sk_storage_map, sk),
PTR_TO_BTF_ID_OR_NULL },
{ offsetof(struct bpf_iter__bpf_sk_storage_map, value),
- PTR_TO_RDWR_BUF | PTR_MAYBE_NULL },
+ PTR_TO_BUF | PTR_MAYBE_NULL },
},
.seq_info = &iter_seq_info,
};
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -1575,7 +1575,7 @@ static struct bpf_iter_reg sock_map_iter
.ctx_arg_info_size = 2,
.ctx_arg_info = {
{ offsetof(struct bpf_iter__sockmap, key),
- PTR_TO_RDONLY_BUF | PTR_MAYBE_NULL },
+ PTR_TO_BUF | PTR_MAYBE_NULL | MEM_RDONLY },
{ offsetof(struct bpf_iter__sockmap, sk),
PTR_TO_BTF_ID_OR_NULL },
},