diff options
author | Joanne Koong <joannelkoong@gmail.com> | 2022-05-23 14:07:11 -0700 |
---|---|---|
committer | Andrii Nakryiko <andrii@kernel.org> | 2022-05-23 14:31:28 -0700 |
commit | 34d4ef5775f776ec4b0d53a02d588bf3195cada6 (patch) | |
tree | 4d71bdf2f9ea5fafa45995ae59d4893eebd1c26c | |
parent | 13bbbfbea7598ea9f8d9c3d73bf053bb57f9c4b2 (diff) | |
download | linux-34d4ef5775f776ec4b0d53a02d588bf3195cada6.tar.bz2 |
bpf: Add dynptr data slices
This patch adds a new helper function
void *bpf_dynptr_data(struct bpf_dynptr *ptr, u32 offset, u32 len);
which returns a pointer to the underlying data of a dynptr. *len*
must be a statically known value. The bpf program may access the returned
data slice as a normal buffer (eg can do direct reads and writes), since
the verifier associates the length with the returned pointer, and
enforces that no out of bounds accesses occur.
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20220523210712.3641569-6-joannelkoong@gmail.com
-rw-r--r-- | include/linux/bpf.h | 1 | ||||
-rw-r--r-- | include/uapi/linux/bpf.h | 12 | ||||
-rw-r--r-- | kernel/bpf/helpers.c | 28 | ||||
-rw-r--r-- | kernel/bpf/verifier.c | 23 | ||||
-rw-r--r-- | tools/include/uapi/linux/bpf.h | 12 |
5 files changed, 76 insertions, 0 deletions
diff --git a/include/linux/bpf.h b/include/linux/bpf.h index c72321b6f306..a7080c86fa76 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -488,6 +488,7 @@ enum bpf_return_type { 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 | MEM_ALLOC | RET_PTR_TO_ALLOC_MEM, + RET_PTR_TO_DYNPTR_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 diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index efe2505650e6..f4009dbdf62d 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -5238,6 +5238,17 @@ union bpf_attr { * 0 on success, -E2BIG if *offset* + *len* exceeds the length * of *dst*'s data, -EINVAL if *dst* is an invalid dynptr or if *dst* * is a read-only dynptr. + * + * void *bpf_dynptr_data(struct bpf_dynptr *ptr, u32 offset, u32 len) + * Description + * Get a pointer to the underlying dynptr data. + * + * *len* must be a statically known value. The returned data slice + * is invalidated whenever the dynptr is invalidated. + * Return + * Pointer to the underlying dynptr data, NULL if the dynptr is + * read-only, if the dynptr is invalid, or if the offset and length + * is out of bounds. */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -5443,6 +5454,7 @@ union bpf_attr { FN(ringbuf_discard_dynptr), \ FN(dynptr_read), \ FN(dynptr_write), \ + FN(dynptr_data), \ /* */ /* integer value in 'imm' field of BPF_CALL instruction selects which helper diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 8cef3fb0d143..225806a02efb 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -1549,6 +1549,32 @@ const struct bpf_func_proto bpf_dynptr_write_proto = { .arg4_type = ARG_CONST_SIZE_OR_ZERO, }; +BPF_CALL_3(bpf_dynptr_data, struct bpf_dynptr_kern *, ptr, u32, offset, u32, len) +{ + int err; + + if (!ptr->data) + return 0; + + err = bpf_dynptr_check_off_len(ptr, offset, len); + if (err) + return 0; + + if (bpf_dynptr_is_rdonly(ptr)) + return 0; + + return (unsigned long)(ptr->data + ptr->offset + offset); +} + +const struct bpf_func_proto bpf_dynptr_data_proto = { + .func = bpf_dynptr_data, + .gpl_only = false, + .ret_type = RET_PTR_TO_DYNPTR_MEM_OR_NULL, + .arg1_type = ARG_PTR_TO_DYNPTR, + .arg2_type = ARG_ANYTHING, + .arg3_type = ARG_CONST_ALLOC_SIZE_OR_ZERO, +}; + const struct bpf_func_proto bpf_get_current_task_proto __weak; const struct bpf_func_proto bpf_get_current_task_btf_proto __weak; const struct bpf_func_proto bpf_probe_read_user_proto __weak; @@ -1615,6 +1641,8 @@ bpf_base_func_proto(enum bpf_func_id func_id) return &bpf_dynptr_read_proto; case BPF_FUNC_dynptr_write: return &bpf_dynptr_write_proto; + case BPF_FUNC_dynptr_data: + return &bpf_dynptr_data_proto; default: break; } diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 8be140351966..aedac2ac02b9 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -5832,6 +5832,14 @@ int check_func_arg_reg_off(struct bpf_verifier_env *env, return __check_ptr_off_reg(env, reg, regno, fixed_off_ok); } +static u32 stack_slot_get_id(struct bpf_verifier_env *env, struct bpf_reg_state *reg) +{ + struct bpf_func_state *state = func(env, reg); + int spi = get_spi(reg->off); + + return state->stack[spi].spilled_ptr.id; +} + static int check_func_arg(struct bpf_verifier_env *env, u32 arg, struct bpf_call_arg_meta *meta, const struct bpf_func_proto *fn) @@ -7384,6 +7392,21 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn regs[BPF_REG_0].id = id; /* For release_reference() */ regs[BPF_REG_0].ref_obj_id = id; + } else if (func_id == BPF_FUNC_dynptr_data) { + int dynptr_id = 0, i; + + /* Find the id of the dynptr we're acquiring a reference to */ + for (i = 0; i < MAX_BPF_FUNC_REG_ARGS; i++) { + if (arg_type_is_dynptr(fn->arg_type[i])) { + if (dynptr_id) { + verbose(env, "verifier internal error: multiple dynptr args in func\n"); + return -EFAULT; + } + dynptr_id = stack_slot_get_id(env, ®s[BPF_REG_1 + i]); + } + } + /* For release_reference() */ + regs[BPF_REG_0].ref_obj_id = dynptr_id; } do_refine_retval_range(regs, fn->ret_type, func_id, &meta); diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index efe2505650e6..f4009dbdf62d 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -5238,6 +5238,17 @@ union bpf_attr { * 0 on success, -E2BIG if *offset* + *len* exceeds the length * of *dst*'s data, -EINVAL if *dst* is an invalid dynptr or if *dst* * is a read-only dynptr. + * + * void *bpf_dynptr_data(struct bpf_dynptr *ptr, u32 offset, u32 len) + * Description + * Get a pointer to the underlying dynptr data. + * + * *len* must be a statically known value. The returned data slice + * is invalidated whenever the dynptr is invalidated. + * Return + * Pointer to the underlying dynptr data, NULL if the dynptr is + * read-only, if the dynptr is invalid, or if the offset and length + * is out of bounds. */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -5443,6 +5454,7 @@ union bpf_attr { FN(ringbuf_discard_dynptr), \ FN(dynptr_read), \ FN(dynptr_write), \ + FN(dynptr_data), \ /* */ /* integer value in 'imm' field of BPF_CALL instruction selects which helper |