[PATCH 5.15 04/33] bpf: Replace RET_XXX_OR_NULL with RET_XXX | PTR_MAYBE_NULL

From: Greg Kroah-Hartman
Date: Fri Apr 29 2022 - 06:46:15 EST

From: Hao Luo <haoluo@xxxxxxxxxx>

commit 3c4807322660d4290ac9062c034aed6b87243861 upstream.

We have introduced a new type to make bpf_ret composable, by
reserving high bits to represent flags.

One of the flag is PTR_MAYBE_NULL, which indicates a pointer
may be NULL. When applying this flag to ret_types, it means
the returned value could be a NULL pointer. This patch
switches the qualified arg_types to use this flag.
The ret_types changed in this patch include:

1. RET_PTR_TO_MAP_VALUE_OR_NULL
2. RET_PTR_TO_SOCKET_OR_NULL
3. RET_PTR_TO_TCP_SOCK_OR_NULL
4. RET_PTR_TO_SOCK_COMMON_OR_NULL
5. RET_PTR_TO_ALLOC_MEM_OR_NULL
6. RET_PTR_TO_MEM_OR_BTF_ID_OR_NULL
7. RET_PTR_TO_BTF_ID_OR_NULL

This patch doesn't eliminate the use of these names, instead
it makes them aliases to 'RET_PTR_TO_XXX | PTR_MAYBE_NULL'.

Signed-off-by: Hao Luo <haoluo@xxxxxxxxxx>
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Link: https://lore.kernel.org/bpf/20211217003152.48334-4-haoluo@xxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx # 5.15.x
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/linux/bpf.h | 19 +++++++++++-------
kernel/bpf/helpers.c | 2 -
kernel/bpf/verifier.c | 52 +++++++++++++++++++++++++-------------------------
3 files changed, 39 insertions(+), 34 deletions(-)

--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -378,17 +378,22 @@ enum bpf_return_type {
RET_INTEGER, /* function returns integer */
RET_VOID, /* function doesn't return anything */
RET_PTR_TO_MAP_VALUE, /* returns a pointer to map elem value */
- RET_PTR_TO_MAP_VALUE_OR_NULL, /* returns a pointer to map elem value or NULL */
- RET_PTR_TO_SOCKET_OR_NULL, /* returns a pointer to a socket or NULL */
- RET_PTR_TO_TCP_SOCK_OR_NULL, /* returns a pointer to a tcp_sock or NULL */
- RET_PTR_TO_SOCK_COMMON_OR_NULL, /* returns a pointer to a sock_common or NULL */
- RET_PTR_TO_ALLOC_MEM_OR_NULL, /* returns a pointer to dynamically allocated memory or NULL */
- RET_PTR_TO_BTF_ID_OR_NULL, /* returns a pointer to a btf_id or NULL */
- RET_PTR_TO_MEM_OR_BTF_ID_OR_NULL, /* returns a pointer to a valid memory or a btf_id or NULL */
+ RET_PTR_TO_SOCKET, /* returns a pointer to a socket */
+ RET_PTR_TO_TCP_SOCK, /* returns a pointer to a tcp_sock */
+ RET_PTR_TO_SOCK_COMMON, /* returns a pointer to a sock_common */
+ RET_PTR_TO_ALLOC_MEM, /* returns a pointer to dynamically allocated memory */
RET_PTR_TO_MEM_OR_BTF_ID, /* returns a pointer to a valid memory or a btf_id */
RET_PTR_TO_BTF_ID, /* returns a pointer to a btf_id */
__BPF_RET_TYPE_MAX,

+ /* Extended ret_types. */
+ RET_PTR_TO_MAP_VALUE_OR_NULL = PTR_MAYBE_NULL | RET_PTR_TO_MAP_VALUE,
+ RET_PTR_TO_SOCKET_OR_NULL = PTR_MAYBE_NULL | RET_PTR_TO_SOCKET,
+ RET_PTR_TO_TCP_SOCK_OR_NULL = PTR_MAYBE_NULL | RET_PTR_TO_TCP_SOCK,
+ RET_PTR_TO_SOCK_COMMON_OR_NULL = PTR_MAYBE_NULL | RET_PTR_TO_SOCK_COMMON,
+ RET_PTR_TO_ALLOC_MEM_OR_NULL = PTR_MAYBE_NULL | RET_PTR_TO_ALLOC_MEM,
+ RET_PTR_TO_BTF_ID_OR_NULL = PTR_MAYBE_NULL | RET_PTR_TO_BTF_ID,
+
/* This must be the last entry. Its purpose is to ensure the enum is
* wide enough to hold the higher bits reserved for bpf_type_flag.
*/
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -667,7 +667,7 @@ BPF_CALL_2(bpf_per_cpu_ptr, const void *
const struct bpf_func_proto bpf_per_cpu_ptr_proto = {
.func = bpf_per_cpu_ptr,
.gpl_only = false,
- .ret_type = RET_PTR_TO_MEM_OR_BTF_ID_OR_NULL,
+ .ret_type = RET_PTR_TO_MEM_OR_BTF_ID | PTR_MAYBE_NULL,
.arg1_type = ARG_PTR_TO_PERCPU_BTF_ID,
.arg2_type = ARG_ANYTHING,
};
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -6195,6 +6195,7 @@ static int check_helper_call(struct bpf_
int *insn_idx_p)
{
const struct bpf_func_proto *fn = NULL;
+ enum bpf_return_type ret_type;
struct bpf_reg_state *regs;
struct bpf_call_arg_meta meta;
int insn_idx = *insn_idx_p;
@@ -6328,13 +6329,13 @@ static int check_helper_call(struct bpf_
regs[BPF_REG_0].subreg_def = DEF_NOT_SUBREG;

/* update return register (already marked as written above) */
- if (fn->ret_type == RET_INTEGER) {
+ ret_type = fn->ret_type;
+ if (ret_type == RET_INTEGER) {
/* sets type to SCALAR_VALUE */
mark_reg_unknown(env, regs, BPF_REG_0);
- } else if (fn->ret_type == RET_VOID) {
+ } else if (ret_type == RET_VOID) {
regs[BPF_REG_0].type = NOT_INIT;
- } else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL ||
- fn->ret_type == RET_PTR_TO_MAP_VALUE) {
+ } else if (base_type(ret_type) == RET_PTR_TO_MAP_VALUE) {
/* There is no offset yet applied, variable or fixed */
mark_reg_known_zero(env, regs, BPF_REG_0);
/* remember map_ptr, so that check_map_access()
@@ -6348,28 +6349,27 @@ static int check_helper_call(struct bpf_
}
regs[BPF_REG_0].map_ptr = meta.map_ptr;
regs[BPF_REG_0].map_uid = meta.map_uid;
- if (fn->ret_type == RET_PTR_TO_MAP_VALUE) {
+ if (type_may_be_null(ret_type)) {
+ regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL;
+ } else {
regs[BPF_REG_0].type = PTR_TO_MAP_VALUE;
if (map_value_has_spin_lock(meta.map_ptr))
regs[BPF_REG_0].id = ++env->id_gen;
- } else {
- regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL;
}
- } else if (fn->ret_type == RET_PTR_TO_SOCKET_OR_NULL) {
+ } else if (base_type(ret_type) == RET_PTR_TO_SOCKET) {
mark_reg_known_zero(env, regs, BPF_REG_0);
regs[BPF_REG_0].type = PTR_TO_SOCKET_OR_NULL;
- } else if (fn->ret_type == RET_PTR_TO_SOCK_COMMON_OR_NULL) {
+ } else if (base_type(ret_type) == RET_PTR_TO_SOCK_COMMON) {
mark_reg_known_zero(env, regs, BPF_REG_0);
regs[BPF_REG_0].type = PTR_TO_SOCK_COMMON_OR_NULL;
- } else if (fn->ret_type == RET_PTR_TO_TCP_SOCK_OR_NULL) {
+ } else if (base_type(ret_type) == RET_PTR_TO_TCP_SOCK) {
mark_reg_known_zero(env, regs, BPF_REG_0);
regs[BPF_REG_0].type = PTR_TO_TCP_SOCK_OR_NULL;
- } else if (fn->ret_type == RET_PTR_TO_ALLOC_MEM_OR_NULL) {
+ } else if (base_type(ret_type) == RET_PTR_TO_ALLOC_MEM) {
mark_reg_known_zero(env, regs, BPF_REG_0);
regs[BPF_REG_0].type = PTR_TO_MEM_OR_NULL;
regs[BPF_REG_0].mem_size = meta.mem_size;
- } else if (fn->ret_type == RET_PTR_TO_MEM_OR_BTF_ID_OR_NULL ||
- fn->ret_type == RET_PTR_TO_MEM_OR_BTF_ID) {
+ } else if (base_type(ret_type) == RET_PTR_TO_MEM_OR_BTF_ID) {
const struct btf_type *t;

mark_reg_known_zero(env, regs, BPF_REG_0);
@@ -6388,28 +6388,28 @@ static int check_helper_call(struct bpf_
return -EINVAL;
}
regs[BPF_REG_0].type =
- fn->ret_type == RET_PTR_TO_MEM_OR_BTF_ID ?
- PTR_TO_MEM : PTR_TO_MEM_OR_NULL;
+ (ret_type & PTR_MAYBE_NULL) ?
+ PTR_TO_MEM_OR_NULL : PTR_TO_MEM;
regs[BPF_REG_0].mem_size = tsize;
} else {
regs[BPF_REG_0].type =
- fn->ret_type == RET_PTR_TO_MEM_OR_BTF_ID ?
- PTR_TO_BTF_ID : PTR_TO_BTF_ID_OR_NULL;
+ (ret_type & PTR_MAYBE_NULL) ?
+ PTR_TO_BTF_ID_OR_NULL : PTR_TO_BTF_ID;
regs[BPF_REG_0].btf = meta.ret_btf;
regs[BPF_REG_0].btf_id = meta.ret_btf_id;
}
- } else if (fn->ret_type == RET_PTR_TO_BTF_ID_OR_NULL ||
- fn->ret_type == RET_PTR_TO_BTF_ID) {
+ } else if (base_type(ret_type) == RET_PTR_TO_BTF_ID) {
int ret_btf_id;

mark_reg_known_zero(env, regs, BPF_REG_0);
- regs[BPF_REG_0].type = fn->ret_type == RET_PTR_TO_BTF_ID ?
- PTR_TO_BTF_ID :
- PTR_TO_BTF_ID_OR_NULL;
+ regs[BPF_REG_0].type = (ret_type & PTR_MAYBE_NULL) ?
+ PTR_TO_BTF_ID_OR_NULL :
+ PTR_TO_BTF_ID;
ret_btf_id = *fn->ret_btf_id;
if (ret_btf_id == 0) {
- verbose(env, "invalid return type %d of func %s#%d\n",
- fn->ret_type, func_id_name(func_id), func_id);
+ verbose(env, "invalid return type %u of func %s#%d\n",
+ base_type(ret_type), func_id_name(func_id),
+ func_id);
return -EINVAL;
}
/* current BPF helper definitions are only coming from
@@ -6418,8 +6418,8 @@ static int check_helper_call(struct bpf_
regs[BPF_REG_0].btf = btf_vmlinux;
regs[BPF_REG_0].btf_id = ret_btf_id;
} else {
- verbose(env, "unknown return type %d of func %s#%d\n",
- fn->ret_type, func_id_name(func_id), func_id);
+ verbose(env, "unknown return type %u of func %s#%d\n",
+ base_type(ret_type), func_id_name(func_id), func_id);
return -EINVAL;
}