diff mbox series

bpf: Fix unsigned 'datasec_id' compared with zero in check_pseudo_btf_id

Message ID 1605009019-22310-1-git-send-email-kaixuxia@tencent.com
State New
Headers show
Series bpf: Fix unsigned 'datasec_id' compared with zero in check_pseudo_btf_id | expand

Commit Message

kaixuxia Nov. 10, 2020, 11:50 a.m. UTC
From: Kaixu Xia <kaixuxia@tencent.com>

The unsigned variable datasec_id is assigned a return value from the call
to check_pseudo_btf_id(), which may return negative error code.

Fixes coccicheck warning:

./kernel/bpf/verifier.c:9616:5-15: WARNING: Unsigned expression compared with zero: datasec_id > 0

Reported-by: Tosk Robot <tencent_os_robot@tencent.com>
Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
---
 kernel/bpf/verifier.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Denis Kirjanov Nov. 10, 2020, 1:02 p.m. UTC | #1
On 11/10/20, xiakaixu1987@gmail.com <xiakaixu1987@gmail.com> wrote:
> From: Kaixu Xia <kaixuxia@tencent.com>
>
> The unsigned variable datasec_id is assigned a return value from the call
> to check_pseudo_btf_id(), which may return negative error code.
>
> Fixes coccicheck warning:
>
> ./kernel/bpf/verifier.c:9616:5-15: WARNING: Unsigned expression compared
> with zero: datasec_id > 0
>
> Reported-by: Tosk Robot <tencent_os_robot@tencent.com>
> Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
> ---
>  kernel/bpf/verifier.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 6200519582a6..e9d8d4309bb4 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -9572,7 +9572,7 @@ static int check_pseudo_btf_id(struct bpf_verifier_env
> *env,
>  			       struct bpf_insn *insn,
>  			       struct bpf_insn_aux_data *aux)
>  {
> -	u32 datasec_id, type, id = insn->imm;
> +	s32 datasec_id, type, id = insn->imm;

but the value is passed as u32 to btf_type_by_id()...

btf_find_by_name_kind() returns s32


>  	const struct btf_var_secinfo *vsi;
>  	const struct btf_type *datasec;
>  	const struct btf_type *t;
> --
> 2.20.0
>
>
Andrii Nakryiko Nov. 10, 2020, 6:41 p.m. UTC | #2
On Tue, Nov 10, 2020 at 3:50 AM <xiakaixu1987@gmail.com> wrote:
>
> From: Kaixu Xia <kaixuxia@tencent.com>
>
> The unsigned variable datasec_id is assigned a return value from the call
> to check_pseudo_btf_id(), which may return negative error code.
>
> Fixes coccicheck warning:
>
> ./kernel/bpf/verifier.c:9616:5-15: WARNING: Unsigned expression compared with zero: datasec_id > 0
>
> Reported-by: Tosk Robot <tencent_os_robot@tencent.com>
> Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
> ---
>  kernel/bpf/verifier.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 6200519582a6..e9d8d4309bb4 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -9572,7 +9572,7 @@ static int check_pseudo_btf_id(struct bpf_verifier_env *env,
>                                struct bpf_insn *insn,
>                                struct bpf_insn_aux_data *aux)
>  {
> -       u32 datasec_id, type, id = insn->imm;
> +       s32 datasec_id, type, id = insn->imm;

you are changing types for type and id variables here, so split out
datasec_id definition into a separate line

>         const struct btf_var_secinfo *vsi;
>         const struct btf_type *datasec;
>         const struct btf_type *t;
> --
> 2.20.0
>
Andrii Nakryiko Nov. 10, 2020, 6:42 p.m. UTC | #3
On Tue, Nov 10, 2020 at 5:02 AM Denis Kirjanov <kda@linux-powerpc.org> wrote:
>
> On 11/10/20, xiakaixu1987@gmail.com <xiakaixu1987@gmail.com> wrote:
> > From: Kaixu Xia <kaixuxia@tencent.com>
> >
> > The unsigned variable datasec_id is assigned a return value from the call
> > to check_pseudo_btf_id(), which may return negative error code.
> >
> > Fixes coccicheck warning:
> >
> > ./kernel/bpf/verifier.c:9616:5-15: WARNING: Unsigned expression compared
> > with zero: datasec_id > 0
> >
> > Reported-by: Tosk Robot <tencent_os_robot@tencent.com>
> > Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
> > ---
> >  kernel/bpf/verifier.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index 6200519582a6..e9d8d4309bb4 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -9572,7 +9572,7 @@ static int check_pseudo_btf_id(struct bpf_verifier_env
> > *env,
> >                              struct bpf_insn *insn,
> >                              struct bpf_insn_aux_data *aux)
> >  {
> > -     u32 datasec_id, type, id = insn->imm;
> > +     s32 datasec_id, type, id = insn->imm;
>
> but the value is passed as u32 to btf_type_by_id()...
>
> btf_find_by_name_kind() returns s32

Right, valid range of BTF type IDs are >= 0 and (significantly) less
than INT_MAX. So s32 is used to signal valid BTF ID or negative error,
but all the APIs accepting BTF ID accept it as just u32.

>
>
> >       const struct btf_var_secinfo *vsi;
> >       const struct btf_type *datasec;
> >       const struct btf_type *t;
> > --
> > 2.20.0
> >
> >
diff mbox series

Patch

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 6200519582a6..e9d8d4309bb4 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -9572,7 +9572,7 @@  static int check_pseudo_btf_id(struct bpf_verifier_env *env,
 			       struct bpf_insn *insn,
 			       struct bpf_insn_aux_data *aux)
 {
-	u32 datasec_id, type, id = insn->imm;
+	s32 datasec_id, type, id = insn->imm;
 	const struct btf_var_secinfo *vsi;
 	const struct btf_type *datasec;
 	const struct btf_type *t;