From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
To: bpf@vger.kernel.org
Cc: "Alexei Starovoitov" <ast@kernel.org>,
"Andrii Nakryiko" <andrii@kernel.org>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Toke Høiland-Jørgensen" <toke@redhat.com>,
"Jesper Dangaard Brouer" <brouer@redhat.com>
Subject: [PATCH bpf-next v2 06/15] bpf: Allow storing user kptr in map
Date: Thu, 17 Mar 2022 17:29:48 +0530 [thread overview]
Message-ID: <20220317115957.3193097-7-memxor@gmail.com> (raw)
In-Reply-To: <20220317115957.3193097-1-memxor@gmail.com>
Recently, verifier gained __user annotation support [0] where it
prevents BPF program from normally derefering user memory pointer in the
kernel, and instead requires use of bpf_probe_read_user. We can allow
the user to also store these pointers in BPF maps, with the logic that
whenever user loads it from the BPF map, it gets marked as MEM_USER. The
tag 'kptr_user' is used to tag such pointers.
[0]: https://lore.kernel.org/bpf/20220127154555.650886-1-yhs@fb.com
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
include/linux/bpf.h | 1 +
kernel/bpf/btf.c | 13 ++++++++++---
kernel/bpf/verifier.c | 15 ++++++++++++---
3 files changed, 23 insertions(+), 6 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 433f5cb161cf..989f47334215 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -163,6 +163,7 @@ enum {
enum {
BPF_MAP_VALUE_OFF_F_REF = (1U << 0),
BPF_MAP_VALUE_OFF_F_PERCPU = (1U << 1),
+ BPF_MAP_VALUE_OFF_F_USER = (1U << 2),
};
struct bpf_map_value_off_desc {
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 04d604931f59..12a89e55e77b 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3197,7 +3197,7 @@ static int btf_find_field_kptr(const struct btf *btf, const struct btf_type *t,
u32 off, int sz, struct btf_field_info *info,
int info_cnt, int idx)
{
- bool kptr_tag = false, kptr_ref_tag = false, kptr_percpu_tag = false;
+ bool kptr_tag = false, kptr_ref_tag = false, kptr_percpu_tag = false, kptr_user_tag = false;
int tags;
/* For PTR, sz is always == 8 */
@@ -3221,12 +3221,17 @@ static int btf_find_field_kptr(const struct btf *btf, const struct btf_type *t,
if (kptr_percpu_tag)
return -EEXIST;
kptr_percpu_tag = true;
+ } else if (!strcmp("kptr_user", __btf_name_by_offset(btf, t->name_off))) {
+ /* repeated tag */
+ if (kptr_user_tag)
+ return -EEXIST;
+ kptr_user_tag = true;
}
/* Look for next tag */
t = btf_type_by_id(btf, t->type);
}
- tags = kptr_tag + kptr_ref_tag + kptr_percpu_tag;
+ tags = kptr_tag + kptr_ref_tag + kptr_percpu_tag + kptr_user_tag;
if (!tags)
return BTF_FIELD_IGNORE;
else if (tags > 1)
@@ -3241,7 +3246,9 @@ static int btf_find_field_kptr(const struct btf *btf, const struct btf_type *t,
if (idx >= info_cnt)
return -E2BIG;
- if (kptr_percpu_tag)
+ if (kptr_user_tag)
+ info[idx].flags = BPF_MAP_VALUE_OFF_F_USER;
+ else if (kptr_percpu_tag)
info[idx].flags = BPF_MAP_VALUE_OFF_F_PERCPU;
else if (kptr_ref_tag)
info[idx].flags = BPF_MAP_VALUE_OFF_F_REF;
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index cc8f7250e43e..5325cc37797a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3521,7 +3521,11 @@ static int map_kptr_match_type(struct bpf_verifier_env *env,
const char *reg_name = "";
bool fixed_off_ok = true;
- if (off_desc->flags & BPF_MAP_VALUE_OFF_F_PERCPU) {
+ if (off_desc->flags & BPF_MAP_VALUE_OFF_F_USER) {
+ if (reg->type != (PTR_TO_BTF_ID | MEM_USER) &&
+ reg->type != (PTR_TO_BTF_ID | PTR_MAYBE_NULL | MEM_USER))
+ goto bad_type;
+ } else if (off_desc->flags & BPF_MAP_VALUE_OFF_F_PERCPU) {
if (reg->type != (PTR_TO_BTF_ID | MEM_PERCPU) &&
reg->type != (PTR_TO_BTF_ID | PTR_MAYBE_NULL | MEM_PERCPU))
goto bad_type;
@@ -3565,7 +3569,9 @@ static int map_kptr_match_type(struct bpf_verifier_env *env,
goto bad_type;
return 0;
bad_type:
- if (off_desc->flags & BPF_MAP_VALUE_OFF_F_PERCPU)
+ if (off_desc->flags & BPF_MAP_VALUE_OFF_F_USER)
+ reg_type = PTR_TO_BTF_ID | PTR_MAYBE_NULL | MEM_USER;
+ else if (off_desc->flags & BPF_MAP_VALUE_OFF_F_PERCPU)
reg_type = PTR_TO_BTF_ID | PTR_MAYBE_NULL | MEM_PERCPU;
else
reg_type = PTR_TO_BTF_ID | PTR_MAYBE_NULL;
@@ -3583,9 +3589,9 @@ static int check_map_kptr_access(struct bpf_verifier_env *env, u32 regno,
enum bpf_access_type t, int insn_idx)
{
struct bpf_reg_state *reg = reg_state(env, regno), *val_reg;
+ bool ref_ptr = false, percpu_ptr = false, user_ptr = false;
struct bpf_insn *insn = &env->prog->insnsi[insn_idx];
enum bpf_type_flag reg_flags = PTR_MAYBE_NULL;
- bool ref_ptr = false, percpu_ptr = false;
struct bpf_map_value_off_desc *off_desc;
int insn_class = BPF_CLASS(insn->code);
struct bpf_map *map = reg->map_ptr;
@@ -3615,8 +3621,11 @@ static int check_map_kptr_access(struct bpf_verifier_env *env, u32 regno,
ref_ptr = off_desc->flags & BPF_MAP_VALUE_OFF_F_REF;
percpu_ptr = off_desc->flags & BPF_MAP_VALUE_OFF_F_PERCPU;
+ user_ptr = off_desc->flags & BPF_MAP_VALUE_OFF_F_USER;
if (percpu_ptr)
reg_flags |= MEM_PERCPU;
+ else if (user_ptr)
+ reg_flags |= MEM_USER;
if (insn_class == BPF_LDX) {
if (WARN_ON_ONCE(value_regno < 0))
--
2.35.1
next prev parent reply other threads:[~2022-03-17 12:00 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-17 11:59 [PATCH bpf-next v2 00/15] Introduce typed pointer support in BPF maps Kumar Kartikeya Dwivedi
2022-03-17 11:59 ` [PATCH bpf-next v2 01/15] bpf: Factor out fd returning from bpf_btf_find_by_name_kind Kumar Kartikeya Dwivedi
2022-03-17 11:59 ` [PATCH bpf-next v2 02/15] bpf: Make btf_find_field more generic Kumar Kartikeya Dwivedi
2022-03-19 17:55 ` Alexei Starovoitov
2022-03-19 19:31 ` Kumar Kartikeya Dwivedi
2022-03-19 20:06 ` Kumar Kartikeya Dwivedi
2022-03-19 21:30 ` Alexei Starovoitov
2022-03-17 11:59 ` [PATCH bpf-next v2 03/15] bpf: Allow storing unreferenced kptr in map Kumar Kartikeya Dwivedi
2022-03-19 18:15 ` Alexei Starovoitov
2022-03-19 18:52 ` Kumar Kartikeya Dwivedi
2022-03-19 21:17 ` Alexei Starovoitov
2022-03-19 21:39 ` Kumar Kartikeya Dwivedi
2022-03-19 21:50 ` Kumar Kartikeya Dwivedi
2022-03-19 22:57 ` Alexei Starovoitov
2022-03-17 11:59 ` [PATCH bpf-next v2 04/15] bpf: Allow storing referenced " Kumar Kartikeya Dwivedi
2022-03-19 18:24 ` Alexei Starovoitov
2022-03-19 18:59 ` Kumar Kartikeya Dwivedi
2022-03-19 21:23 ` Alexei Starovoitov
2022-03-19 21:43 ` Kumar Kartikeya Dwivedi
2022-03-20 0:57 ` Kumar Kartikeya Dwivedi
2022-03-17 11:59 ` [PATCH bpf-next v2 05/15] bpf: Allow storing percpu " Kumar Kartikeya Dwivedi
2022-03-19 18:30 ` Alexei Starovoitov
2022-03-19 19:04 ` Kumar Kartikeya Dwivedi
2022-03-19 21:26 ` Alexei Starovoitov
2022-03-19 21:45 ` Kumar Kartikeya Dwivedi
2022-03-19 23:01 ` Alexei Starovoitov
2022-03-17 11:59 ` Kumar Kartikeya Dwivedi [this message]
2022-03-19 18:28 ` [PATCH bpf-next v2 06/15] bpf: Allow storing user " Alexei Starovoitov
2022-03-19 19:02 ` Kumar Kartikeya Dwivedi
2022-03-17 11:59 ` [PATCH bpf-next v2 07/15] bpf: Prevent escaping of kptr loaded from maps Kumar Kartikeya Dwivedi
2022-03-17 11:59 ` [PATCH bpf-next v2 08/15] bpf: Adapt copy_map_value for multiple offset case Kumar Kartikeya Dwivedi
2022-03-19 18:34 ` Alexei Starovoitov
2022-03-19 19:06 ` Kumar Kartikeya Dwivedi
2022-03-17 11:59 ` [PATCH bpf-next v2 09/15] bpf: Always raise reference in btf_get_module_btf Kumar Kartikeya Dwivedi
2022-03-19 18:43 ` Alexei Starovoitov
2022-03-17 11:59 ` [PATCH bpf-next v2 10/15] bpf: Populate pairs of btf_id and destructor kfunc in btf Kumar Kartikeya Dwivedi
2022-03-17 11:59 ` [PATCH bpf-next v2 11/15] bpf: Wire up freeing of referenced kptr Kumar Kartikeya Dwivedi
2022-03-17 11:59 ` [PATCH bpf-next v2 12/15] bpf: Teach verifier about kptr_get kfunc helpers Kumar Kartikeya Dwivedi
2022-03-17 11:59 ` [PATCH bpf-next v2 13/15] libbpf: Add kptr type tag macros to bpf_helpers.h Kumar Kartikeya Dwivedi
2022-03-17 11:59 ` [PATCH bpf-next v2 14/15] selftests/bpf: Add C tests for kptr Kumar Kartikeya Dwivedi
2022-03-17 11:59 ` [PATCH bpf-next v2 15/15] selftests/bpf: Add verifier " Kumar Kartikeya Dwivedi
2022-03-19 18:50 ` [PATCH bpf-next v2 00/15] Introduce typed pointer support in BPF maps patchwork-bot+netdevbpf
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