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Message-Id: <20230216225524.1192789-4-joannelkoong@gmail.com>
Date: Thu, 16 Feb 2023 14:55:18 -0800
From: Joanne Koong <joannelkoong@...il.com>
To: bpf@...r.kernel.org
Cc: martin.lau@...nel.org, andrii@...nel.org, memxor@...il.com,
ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org,
kernel-team@...com, Joanne Koong <joannelkoong@...il.com>
Subject: [PATCH v10 bpf-next 3/9] bpf: Allow initializing dynptrs in kfuncs
This change allows kfuncs to take in an uninitialized dynptr as a
parameter. Before this change, only helper functions could successfully
use uninitialized dynptrs. This change moves the memory access check
(including stack state growing and slot marking) into
process_dynptr_func(), which both helpers and kfuncs call into.
Signed-off-by: Joanne Koong <joannelkoong@...il.com>
---
kernel/bpf/verifier.c | 67 ++++++++++++++-----------------------------
1 file changed, 22 insertions(+), 45 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 23a7749e8463..de99fa02b8d8 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -268,7 +268,6 @@ struct bpf_call_arg_meta {
u32 ret_btf_id;
u32 subprogno;
struct btf_field *kptr_field;
- u8 uninit_dynptr_regno;
};
struct btf *btf_vmlinux;
@@ -6216,10 +6215,11 @@ static int process_kptr_func(struct bpf_verifier_env *env, int regno,
* Helpers which do not mutate the bpf_dynptr set MEM_RDONLY in their argument
* type, and declare it as 'const struct bpf_dynptr *' in their prototype.
*/
-int process_dynptr_func(struct bpf_verifier_env *env, int regno,
- enum bpf_arg_type arg_type, struct bpf_call_arg_meta *meta)
+int process_dynptr_func(struct bpf_verifier_env *env, int regno, int insn_idx,
+ enum bpf_arg_type arg_type)
{
struct bpf_reg_state *regs = cur_regs(env), *reg = ®s[regno];
+ int err;
/* MEM_UNINIT and MEM_RDONLY are exclusive, when applied to an
* ARG_PTR_TO_DYNPTR (or ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_*):
@@ -6245,23 +6245,23 @@ int process_dynptr_func(struct bpf_verifier_env *env, int regno,
* to.
*/
if (arg_type & MEM_UNINIT) {
+ int i;
+
if (!is_dynptr_reg_valid_uninit(env, reg)) {
verbose(env, "Dynptr has to be an uninitialized dynptr\n");
return -EINVAL;
}
- /* We only support one dynptr being uninitialized at the moment,
- * which is sufficient for the helper functions we have right now.
- */
- if (meta->uninit_dynptr_regno) {
- verbose(env, "verifier internal error: multiple uninitialized dynptr args\n");
- return -EFAULT;
+ /* we write BPF_DW bits (8 bytes) at a time */
+ for (i = 0; i < BPF_DYNPTR_SIZE; i += 8) {
+ err = check_mem_access(env, insn_idx, regno,
+ i, BPF_DW, BPF_WRITE, -1, false);
+ if (err)
+ return err;
}
- meta->uninit_dynptr_regno = regno;
+ err = mark_stack_slots_dynptr(env, reg, arg_type, insn_idx);
} else /* MEM_RDONLY and None case from above */ {
- int err;
-
/* For the reg->type == PTR_TO_STACK case, bpf_dynptr is never const */
if (reg->type == CONST_PTR_TO_DYNPTR && !(arg_type & MEM_RDONLY)) {
verbose(env, "cannot pass pointer to const bpf_dynptr, the helper mutates it\n");
@@ -6297,10 +6297,8 @@ int process_dynptr_func(struct bpf_verifier_env *env, int regno,
}
err = mark_dynptr_read(env, reg);
- if (err)
- return err;
}
- return 0;
+ return err;
}
static bool arg_type_is_mem_size(enum bpf_arg_type type)
@@ -6694,7 +6692,8 @@ static int dynptr_ref_obj_id(struct bpf_verifier_env *env, struct bpf_reg_state
static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
struct bpf_call_arg_meta *meta,
- const struct bpf_func_proto *fn)
+ const struct bpf_func_proto *fn,
+ int insn_idx)
{
u32 regno = BPF_REG_1 + arg;
struct bpf_reg_state *regs = cur_regs(env), *reg = ®s[regno];
@@ -6907,7 +6906,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
err = check_mem_size_reg(env, reg, regno, true, meta);
break;
case ARG_PTR_TO_DYNPTR:
- err = process_dynptr_func(env, regno, arg_type, meta);
+ err = process_dynptr_func(env, regno, insn_idx, arg_type);
if (err)
return err;
break;
@@ -8197,7 +8196,7 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
meta.func_id = func_id;
/* check args */
for (i = 0; i < MAX_BPF_FUNC_REG_ARGS; i++) {
- err = check_func_arg(env, i, &meta, fn);
+ err = check_func_arg(env, i, &meta, fn, insn_idx);
if (err)
return err;
}
@@ -8222,30 +8221,6 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
regs = cur_regs(env);
- /* This can only be set for PTR_TO_STACK, as CONST_PTR_TO_DYNPTR cannot
- * be reinitialized by any dynptr helper. Hence, mark_stack_slots_dynptr
- * is safe to do directly.
- */
- if (meta.uninit_dynptr_regno) {
- if (regs[meta.uninit_dynptr_regno].type == CONST_PTR_TO_DYNPTR) {
- verbose(env, "verifier internal error: CONST_PTR_TO_DYNPTR cannot be initialized\n");
- return -EFAULT;
- }
- /* we write BPF_DW bits (8 bytes) at a time */
- for (i = 0; i < BPF_DYNPTR_SIZE; i += 8) {
- err = check_mem_access(env, insn_idx, meta.uninit_dynptr_regno,
- i, BPF_DW, BPF_WRITE, -1, false);
- if (err)
- return err;
- }
-
- err = mark_stack_slots_dynptr(env, ®s[meta.uninit_dynptr_regno],
- fn->arg_type[meta.uninit_dynptr_regno - BPF_REG_1],
- insn_idx);
- if (err)
- return err;
- }
-
if (meta.release_regno) {
err = -EINVAL;
/* This can only be set for PTR_TO_STACK, as CONST_PTR_TO_DYNPTR cannot
@@ -9455,7 +9430,8 @@ static int process_kf_arg_ptr_to_rbtree_node(struct bpf_verifier_env *env,
&meta->arg_rbtree_root.field);
}
-static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_arg_meta *meta)
+static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_arg_meta *meta,
+ int insn_idx)
{
const char *func_name = meta->func_name, *ref_tname;
const struct btf *btf = meta->btf;
@@ -9652,7 +9628,8 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
return -EINVAL;
}
- ret = process_dynptr_func(env, regno, ARG_PTR_TO_DYNPTR | MEM_RDONLY, NULL);
+ ret = process_dynptr_func(env, regno, insn_idx,
+ ARG_PTR_TO_DYNPTR | MEM_RDONLY);
if (ret < 0)
return ret;
break;
@@ -9860,7 +9837,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
}
/* Check the arguments */
- err = check_kfunc_args(env, &meta);
+ err = check_kfunc_args(env, &meta, insn_idx);
if (err < 0)
return err;
/* In case of release function, we get register number of refcounted
--
2.30.2
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