diff mbox series

[bpf-next,1/3] bpf: consider CONST_PTR_TO_MAP as trusted pointer to struct bpf_map

Message ID 20230714142100.42265-2-aspsk@isovalent.com (mailing list archive)
State Changes Requested
Delegated to: BPF
Headers show
Series [bpf-next,1/3] bpf: consider CONST_PTR_TO_MAP as trusted pointer to struct bpf_map | expand

Checks

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Commit Message

Anton Protopopov July 14, 2023, 2:20 p.m. UTC 
Patch verifier to regard values of type CONST_PTR_TO_MAP as trusted
pointers to struct bpf_map. This allows kfuncs to work with `struct
bpf_map *` arguments.

Save some bytes by defining btf_bpf_map_id as BTF_ID_LIST_GLOBAL_SINGLE
(which is u32[1]), not as BTF_ID_LIST (which is u32[64]).

Signed-off-by: Anton Protopopov <aspsk@isovalent.com>
---
 include/linux/btf_ids.h | 1 +
 kernel/bpf/map_iter.c   | 3 +--
 kernel/bpf/verifier.c   | 5 ++++-
 3 files changed, 6 insertions(+), 3 deletions(-)

Comments

Alexei Starovoitov July 14, 2023, 5:56 p.m. UTC | #1 
On Fri, Jul 14, 2023 at 7:20 AM Anton Protopopov <aspsk@isovalent.com> wrote:
>
> Patch verifier to regard values of type CONST_PTR_TO_MAP as trusted
> pointers to struct bpf_map. This allows kfuncs to work with `struct
> bpf_map *` arguments.
>
> Save some bytes by defining btf_bpf_map_id as BTF_ID_LIST_GLOBAL_SINGLE
> (which is u32[1]), not as BTF_ID_LIST (which is u32[64]).
>
> Signed-off-by: Anton Protopopov <aspsk@isovalent.com>
> ---
>  include/linux/btf_ids.h | 1 +
>  kernel/bpf/map_iter.c   | 3 +--
>  kernel/bpf/verifier.c   | 5 ++++-
>  3 files changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/btf_ids.h b/include/linux/btf_ids.h
> index 00950cc03bff..a3462a9b8e18 100644
> --- a/include/linux/btf_ids.h
> +++ b/include/linux/btf_ids.h
> @@ -267,5 +267,6 @@ MAX_BTF_TRACING_TYPE,
>  extern u32 btf_tracing_ids[];
>  extern u32 bpf_cgroup_btf_id[];
>  extern u32 bpf_local_storage_map_btf_id[];
> +extern u32 btf_bpf_map_id[];
>
>  #endif
> diff --git a/kernel/bpf/map_iter.c b/kernel/bpf/map_iter.c
> index d06d3b7150e5..b67996147895 100644
> --- a/kernel/bpf/map_iter.c
> +++ b/kernel/bpf/map_iter.c
> @@ -78,8 +78,7 @@ static const struct seq_operations bpf_map_seq_ops = {
>         .show   = bpf_map_seq_show,
>  };
>
> -BTF_ID_LIST(btf_bpf_map_id)
> -BTF_ID(struct, bpf_map)
> +BTF_ID_LIST_GLOBAL_SINGLE(btf_bpf_map_id, struct, bpf_map)
>
>  static const struct bpf_iter_seq_info bpf_map_seq_info = {
>         .seq_ops                = &bpf_map_seq_ops,
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 0b9da95331d7..5663f97ef292 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -5419,6 +5419,9 @@ static bool is_trusted_reg(const struct bpf_reg_state *reg)
>         if (reg->ref_obj_id)
>                 return true;
>
> +       if (reg->type == CONST_PTR_TO_MAP)
> +               return true;
> +

Overall it looks great.
Instead of above, how about the following instead:

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 0b9da95331d7..cd08167dc347 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -10775,7 +10775,7 @@ static int check_kfunc_args(struct
bpf_verifier_env *env, struct bpf_kfunc_call_
                        if (!is_kfunc_trusted_args(meta) && !is_kfunc_rcu(meta))
                                break;

-                       if (!is_trusted_reg(reg)) {
+                       if (!is_trusted_reg(reg) &&
!reg2btf_ids[base_type(reg->type)]) {


This way we won't need to list every convertible type in is_trusted_reg.

I'm a bit hesitant to put reg2btf_ids[] check directly into is_trusted_reg().
Maybe it's ok, but it needs more analysis.
Anton Protopopov July 16, 2023, 7:50 a.m. UTC | #2 
On Fri, Jul 14, 2023 at 10:56:00AM -0700, Alexei Starovoitov wrote:
> On Fri, Jul 14, 2023 at 7:20 AM Anton Protopopov <aspsk@isovalent.com> wrote:
> >
> > Patch verifier to regard values of type CONST_PTR_TO_MAP as trusted
> > pointers to struct bpf_map. This allows kfuncs to work with `struct
> > bpf_map *` arguments.
> >
> > Save some bytes by defining btf_bpf_map_id as BTF_ID_LIST_GLOBAL_SINGLE
> > (which is u32[1]), not as BTF_ID_LIST (which is u32[64]).
> >
> > Signed-off-by: Anton Protopopov <aspsk@isovalent.com>
> > ---
> >  include/linux/btf_ids.h | 1 +
> >  kernel/bpf/map_iter.c   | 3 +--
> >  kernel/bpf/verifier.c   | 5 ++++-
> >  3 files changed, 6 insertions(+), 3 deletions(-)
> >
> > diff --git a/include/linux/btf_ids.h b/include/linux/btf_ids.h
> > index 00950cc03bff..a3462a9b8e18 100644
> > --- a/include/linux/btf_ids.h
> > +++ b/include/linux/btf_ids.h
> > @@ -267,5 +267,6 @@ MAX_BTF_TRACING_TYPE,
> >  extern u32 btf_tracing_ids[];
> >  extern u32 bpf_cgroup_btf_id[];
> >  extern u32 bpf_local_storage_map_btf_id[];
> > +extern u32 btf_bpf_map_id[];
> >
> >  #endif
> > diff --git a/kernel/bpf/map_iter.c b/kernel/bpf/map_iter.c
> > index d06d3b7150e5..b67996147895 100644
> > --- a/kernel/bpf/map_iter.c
> > +++ b/kernel/bpf/map_iter.c
> > @@ -78,8 +78,7 @@ static const struct seq_operations bpf_map_seq_ops = {
> >         .show   = bpf_map_seq_show,
> >  };
> >
> > -BTF_ID_LIST(btf_bpf_map_id)
> > -BTF_ID(struct, bpf_map)
> > +BTF_ID_LIST_GLOBAL_SINGLE(btf_bpf_map_id, struct, bpf_map)
> >
> >  static const struct bpf_iter_seq_info bpf_map_seq_info = {
> >         .seq_ops                = &bpf_map_seq_ops,
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index 0b9da95331d7..5663f97ef292 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -5419,6 +5419,9 @@ static bool is_trusted_reg(const struct bpf_reg_state *reg)
> >         if (reg->ref_obj_id)
> >                 return true;
> >
> > +       if (reg->type == CONST_PTR_TO_MAP)
> > +               return true;
> > +
> 
> Overall it looks great.
> Instead of above, how about the following instead:
> 
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 0b9da95331d7..cd08167dc347 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -10775,7 +10775,7 @@ static int check_kfunc_args(struct
> bpf_verifier_env *env, struct bpf_kfunc_call_
>                         if (!is_kfunc_trusted_args(meta) && !is_kfunc_rcu(meta))
>                                 break;
> 
> -                       if (!is_trusted_reg(reg)) {
> +                       if (!is_trusted_reg(reg) &&
> !reg2btf_ids[base_type(reg->type)]) {
> 
> 
> This way we won't need to list every convertible type in is_trusted_reg.
> 
> I'm a bit hesitant to put reg2btf_ids[] check directly into is_trusted_reg().
> Maybe it's ok, but it needs more analysis.

I am not sure I see a difference in adding a check you proposed above and
adding the reg2btf_ids[] check directly into the is_trusted_reg() function.
Basically, we say "if type is in reg2btf_ids[], then consider it trusted" in
both cases. AFAIS, currently the reg2btf_ids[] contains only trusted types,
however, could it happen that we add a non-trusted type there?

So, I would leave the patch as is (which also makes sense because the
const-ptr-to-map is a special case), or add the "reg2btf_ids[] check" 
directly into the is_trusted_reg() function.
Alexei Starovoitov July 19, 2023, 12:54 a.m. UTC | #3 
On Sun, Jul 16, 2023 at 12:49 AM Anton Protopopov <aspsk@isovalent.com> wrote:
>
> On Fri, Jul 14, 2023 at 10:56:00AM -0700, Alexei Starovoitov wrote:
> > On Fri, Jul 14, 2023 at 7:20 AM Anton Protopopov <aspsk@isovalent.com> wrote:
> > >
> > > Patch verifier to regard values of type CONST_PTR_TO_MAP as trusted
> > > pointers to struct bpf_map. This allows kfuncs to work with `struct
> > > bpf_map *` arguments.
> > >
> > > Save some bytes by defining btf_bpf_map_id as BTF_ID_LIST_GLOBAL_SINGLE
> > > (which is u32[1]), not as BTF_ID_LIST (which is u32[64]).
> > >
> > > Signed-off-by: Anton Protopopov <aspsk@isovalent.com>
> > > ---
> > >  include/linux/btf_ids.h | 1 +
> > >  kernel/bpf/map_iter.c   | 3 +--
> > >  kernel/bpf/verifier.c   | 5 ++++-
> > >  3 files changed, 6 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/include/linux/btf_ids.h b/include/linux/btf_ids.h
> > > index 00950cc03bff..a3462a9b8e18 100644
> > > --- a/include/linux/btf_ids.h
> > > +++ b/include/linux/btf_ids.h
> > > @@ -267,5 +267,6 @@ MAX_BTF_TRACING_TYPE,
> > >  extern u32 btf_tracing_ids[];
> > >  extern u32 bpf_cgroup_btf_id[];
> > >  extern u32 bpf_local_storage_map_btf_id[];
> > > +extern u32 btf_bpf_map_id[];
> > >
> > >  #endif
> > > diff --git a/kernel/bpf/map_iter.c b/kernel/bpf/map_iter.c
> > > index d06d3b7150e5..b67996147895 100644
> > > --- a/kernel/bpf/map_iter.c
> > > +++ b/kernel/bpf/map_iter.c
> > > @@ -78,8 +78,7 @@ static const struct seq_operations bpf_map_seq_ops = {
> > >         .show   = bpf_map_seq_show,
> > >  };
> > >
> > > -BTF_ID_LIST(btf_bpf_map_id)
> > > -BTF_ID(struct, bpf_map)
> > > +BTF_ID_LIST_GLOBAL_SINGLE(btf_bpf_map_id, struct, bpf_map)
> > >
> > >  static const struct bpf_iter_seq_info bpf_map_seq_info = {
> > >         .seq_ops                = &bpf_map_seq_ops,
> > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > > index 0b9da95331d7..5663f97ef292 100644
> > > --- a/kernel/bpf/verifier.c
> > > +++ b/kernel/bpf/verifier.c
> > > @@ -5419,6 +5419,9 @@ static bool is_trusted_reg(const struct bpf_reg_state *reg)
> > >         if (reg->ref_obj_id)
> > >                 return true;
> > >
> > > +       if (reg->type == CONST_PTR_TO_MAP)
> > > +               return true;
> > > +
> >
> > Overall it looks great.
> > Instead of above, how about the following instead:
> >
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index 0b9da95331d7..cd08167dc347 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -10775,7 +10775,7 @@ static int check_kfunc_args(struct
> > bpf_verifier_env *env, struct bpf_kfunc_call_
> >                         if (!is_kfunc_trusted_args(meta) && !is_kfunc_rcu(meta))
> >                                 break;
> >
> > -                       if (!is_trusted_reg(reg)) {
> > +                       if (!is_trusted_reg(reg) &&
> > !reg2btf_ids[base_type(reg->type)]) {
> >
> >
> > This way we won't need to list every convertible type in is_trusted_reg.
> >
> > I'm a bit hesitant to put reg2btf_ids[] check directly into is_trusted_reg().
> > Maybe it's ok, but it needs more analysis.
>
> I am not sure I see a difference in adding a check you proposed above and
> adding the reg2btf_ids[] check directly into the is_trusted_reg() function.
> Basically, we say "if type is in reg2btf_ids[], then consider it trusted" in
> both cases. AFAIS, currently the reg2btf_ids[] contains only trusted types,
> however, could it happen that we add a non-trusted type there?
>
> So, I would leave the patch as is (which also makes sense because the
> const-ptr-to-map is a special case), or add the "reg2btf_ids[] check"
> directly into the is_trusted_reg() function.

Fair enough. Let's add reg2btf_ids[] to is_trusted_reg() directly.
Anton Protopopov July 19, 2023, 7:10 a.m. UTC | #4 
On Tue, Jul 18, 2023 at 05:54:27PM -0700, Alexei Starovoitov wrote:
> On Sun, Jul 16, 2023 at 12:49 AM Anton Protopopov <aspsk@isovalent.com> wrote:
> >
> > On Fri, Jul 14, 2023 at 10:56:00AM -0700, Alexei Starovoitov wrote:
> > > On Fri, Jul 14, 2023 at 7:20 AM Anton Protopopov <aspsk@isovalent.com> wrote:
> > > >
> > > > Patch verifier to regard values of type CONST_PTR_TO_MAP as trusted
> > > > pointers to struct bpf_map. This allows kfuncs to work with `struct
> > > > bpf_map *` arguments.
> > > >
> > > > Save some bytes by defining btf_bpf_map_id as BTF_ID_LIST_GLOBAL_SINGLE
> > > > (which is u32[1]), not as BTF_ID_LIST (which is u32[64]).
> > > >
> > > > Signed-off-by: Anton Protopopov <aspsk@isovalent.com>
> > > > ---
> > > >  include/linux/btf_ids.h | 1 +
> > > >  kernel/bpf/map_iter.c   | 3 +--
> > > >  kernel/bpf/verifier.c   | 5 ++++-
> > > >  3 files changed, 6 insertions(+), 3 deletions(-)
> > > >
> > > > diff --git a/include/linux/btf_ids.h b/include/linux/btf_ids.h
> > > > index 00950cc03bff..a3462a9b8e18 100644
> > > > --- a/include/linux/btf_ids.h
> > > > +++ b/include/linux/btf_ids.h
> > > > @@ -267,5 +267,6 @@ MAX_BTF_TRACING_TYPE,
> > > >  extern u32 btf_tracing_ids[];
> > > >  extern u32 bpf_cgroup_btf_id[];
> > > >  extern u32 bpf_local_storage_map_btf_id[];
> > > > +extern u32 btf_bpf_map_id[];
> > > >
> > > >  #endif
> > > > diff --git a/kernel/bpf/map_iter.c b/kernel/bpf/map_iter.c
> > > > index d06d3b7150e5..b67996147895 100644
> > > > --- a/kernel/bpf/map_iter.c
> > > > +++ b/kernel/bpf/map_iter.c
> > > > @@ -78,8 +78,7 @@ static const struct seq_operations bpf_map_seq_ops = {
> > > >         .show   = bpf_map_seq_show,
> > > >  };
> > > >
> > > > -BTF_ID_LIST(btf_bpf_map_id)
> > > > -BTF_ID(struct, bpf_map)
> > > > +BTF_ID_LIST_GLOBAL_SINGLE(btf_bpf_map_id, struct, bpf_map)
> > > >
> > > >  static const struct bpf_iter_seq_info bpf_map_seq_info = {
> > > >         .seq_ops                = &bpf_map_seq_ops,
> > > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > > > index 0b9da95331d7..5663f97ef292 100644
> > > > --- a/kernel/bpf/verifier.c
> > > > +++ b/kernel/bpf/verifier.c
> > > > @@ -5419,6 +5419,9 @@ static bool is_trusted_reg(const struct bpf_reg_state *reg)
> > > >         if (reg->ref_obj_id)
> > > >                 return true;
> > > >
> > > > +       if (reg->type == CONST_PTR_TO_MAP)
> > > > +               return true;
> > > > +
> > >
> > > Overall it looks great.
> > > Instead of above, how about the following instead:
> > >
> > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > > index 0b9da95331d7..cd08167dc347 100644
> > > --- a/kernel/bpf/verifier.c
> > > +++ b/kernel/bpf/verifier.c
> > > @@ -10775,7 +10775,7 @@ static int check_kfunc_args(struct
> > > bpf_verifier_env *env, struct bpf_kfunc_call_
> > >                         if (!is_kfunc_trusted_args(meta) && !is_kfunc_rcu(meta))
> > >                                 break;
> > >
> > > -                       if (!is_trusted_reg(reg)) {
> > > +                       if (!is_trusted_reg(reg) &&
> > > !reg2btf_ids[base_type(reg->type)]) {
> > >
> > >
> > > This way we won't need to list every convertible type in is_trusted_reg.
> > >
> > > I'm a bit hesitant to put reg2btf_ids[] check directly into is_trusted_reg().
> > > Maybe it's ok, but it needs more analysis.
> >
> > I am not sure I see a difference in adding a check you proposed above and
> > adding the reg2btf_ids[] check directly into the is_trusted_reg() function.
> > Basically, we say "if type is in reg2btf_ids[], then consider it trusted" in
> > both cases. AFAIS, currently the reg2btf_ids[] contains only trusted types,
> > however, could it happen that we add a non-trusted type there?
> >
> > So, I would leave the patch as is (which also makes sense because the
> > const-ptr-to-map is a special case), or add the "reg2btf_ids[] check"
> > directly into the is_trusted_reg() function.
> 
> Fair enough. Let's add reg2btf_ids[] to is_trusted_reg() directly.

Thanks, I will send v2.
diff mbox series

Patch

diff --git a/include/linux/btf_ids.h b/include/linux/btf_ids.h
index 00950cc03bff..a3462a9b8e18 100644
--- a/include/linux/btf_ids.h
+++ b/include/linux/btf_ids.h
@@ -267,5 +267,6 @@  MAX_BTF_TRACING_TYPE,
 extern u32 btf_tracing_ids[];
 extern u32 bpf_cgroup_btf_id[];
 extern u32 bpf_local_storage_map_btf_id[];
+extern u32 btf_bpf_map_id[];
 
 #endif
diff --git a/kernel/bpf/map_iter.c b/kernel/bpf/map_iter.c
index d06d3b7150e5..b67996147895 100644
--- a/kernel/bpf/map_iter.c
+++ b/kernel/bpf/map_iter.c
@@ -78,8 +78,7 @@  static const struct seq_operations bpf_map_seq_ops = {
 	.show	= bpf_map_seq_show,
 };
 
-BTF_ID_LIST(btf_bpf_map_id)
-BTF_ID(struct, bpf_map)
+BTF_ID_LIST_GLOBAL_SINGLE(btf_bpf_map_id, struct, bpf_map)
 
 static const struct bpf_iter_seq_info bpf_map_seq_info = {
 	.seq_ops		= &bpf_map_seq_ops,
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 0b9da95331d7..5663f97ef292 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5419,6 +5419,9 @@  static bool is_trusted_reg(const struct bpf_reg_state *reg)
 	if (reg->ref_obj_id)
 		return true;
 
+	if (reg->type == CONST_PTR_TO_MAP)
+		return true;
+
 	/* If a register is not referenced, it is trusted if it has the
 	 * MEM_ALLOC or PTR_TRUSTED type modifiers, and no others. Some of the
 	 * other type modifiers may be safe, but we elect to take an opt-in
@@ -10052,13 +10055,13 @@  static bool __btf_type_is_scalar_struct(struct bpf_verifier_env *env,
 	return true;
 }
 
-
 static u32 *reg2btf_ids[__BPF_REG_TYPE_MAX] = {
 #ifdef CONFIG_NET
 	[PTR_TO_SOCKET] = &btf_sock_ids[BTF_SOCK_TYPE_SOCK],
 	[PTR_TO_SOCK_COMMON] = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON],
 	[PTR_TO_TCP_SOCK] = &btf_sock_ids[BTF_SOCK_TYPE_TCP],
 #endif
+	[CONST_PTR_TO_MAP] = btf_bpf_map_id,
 };
 
 enum kfunc_ptr_arg_type {