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bpf: Add check_func_arg_reg_off function 

Lift the list of register types allowed for having fixed and variable
offsets when passed as helper function arguments into a common helper,
so that they can be reused for kfunc checks in later commits. Keeping a
common helper aids maintainability and allows us to follow the same
consistent rules across helpers and kfuncs. Also, convert check_func_arg
to use this function.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220304224645.3677453-2-memxor@gmail.com
This commit is contained in:
Kumar Kartikeya Dwivedi 2022-03-05 04:16:38 +05:30 committed by Alexei Starovoitov
parent caec549534
commit 25b35dd281
2 changed files with 44 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
include/linux/bpf_verifier.h
View File

@ -521,6 +521,9 @@ bpf_prog_offload_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt);
int check_ptr_off_reg(struct bpf_verifier_env *env,
const struct bpf_reg_state *reg, int regno);
int check_func_arg_reg_off(struct bpf_verifier_env *env,
const struct bpf_reg_state *reg, int regno,
enum bpf_arg_type arg_type);
int check_kfunc_mem_size_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
u32 regno);
int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,

69
kernel/bpf/verifier.c
View File

@ -5359,6 +5359,44 @@ found:
return 0;
}
int check_func_arg_reg_off(struct bpf_verifier_env *env,
const struct bpf_reg_state *reg, int regno,
enum bpf_arg_type arg_type)
{
enum bpf_reg_type type = reg->type;
bool fixed_off_ok = false;
switch ((u32)type) {
case SCALAR_VALUE:
/* Pointer types where reg offset is explicitly allowed: */
case PTR_TO_PACKET:
case PTR_TO_PACKET_META:
case PTR_TO_MAP_KEY:
case PTR_TO_MAP_VALUE:
case PTR_TO_MEM:
case PTR_TO_MEM | MEM_RDONLY:
case PTR_TO_MEM | MEM_ALLOC:
case PTR_TO_BUF:
case PTR_TO_BUF | MEM_RDONLY:
case PTR_TO_STACK:
/* Some of the argument types nevertheless require a
* zero register offset.
*/
if (arg_type != ARG_PTR_TO_ALLOC_MEM)
return 0;
break;
/* All the rest must be rejected, except PTR_TO_BTF_ID which allows
* fixed offset.
*/
case PTR_TO_BTF_ID:
fixed_off_ok = true;
break;
default:
break;
}
return __check_ptr_off_reg(env, reg, regno, fixed_off_ok);
}
static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
struct bpf_call_arg_meta *meta,
const struct bpf_func_proto *fn)
@ -5408,34 +5446,9 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
if (err)
return err;
switch ((u32)type) {
case SCALAR_VALUE:
/* Pointer types where reg offset is explicitly allowed: */
case PTR_TO_PACKET:
case PTR_TO_PACKET_META:
case PTR_TO_MAP_KEY:
case PTR_TO_MAP_VALUE:
case PTR_TO_MEM:
case PTR_TO_MEM | MEM_RDONLY:
case PTR_TO_MEM | MEM_ALLOC:
case PTR_TO_BUF:
case PTR_TO_BUF | MEM_RDONLY:
case PTR_TO_STACK:
/* Some of the argument types nevertheless require a
* zero register offset.
*/
if (arg_type == ARG_PTR_TO_ALLOC_MEM)
goto force_off_check;
break;
/* All the rest must be rejected: */
default:
force_off_check:
err = __check_ptr_off_reg(env, reg, regno,
type == PTR_TO_BTF_ID);
if (err < 0)
return err;
break;
}
err = check_func_arg_reg_off(env, reg, regno, arg_type);
if (err)
return err;
skip_type_check:
if (reg->ref_obj_id) {