2020-11-11 03:03:42

by Kaixu Xia

Subject: [PATCH v2] bpf: Fix unsigned 'datasec_id' compared with zero in check_pseudo_btf_id

From: Kaixu Xia <[email protected]>

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 <[email protected]>
Signed-off-by: Kaixu Xia <[email protected]>
---
v2:
-split out datasec_id definition into a separate line.

kernel/bpf/verifier.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 6200519582a6..3fea4fc04e94 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -9572,7 +9572,8 @@ 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;
+ u32 type, id = insn->imm;
const struct btf_var_secinfo *vsi;
const struct btf_type *datasec;
const struct btf_type *t;
--
2.20.0

2020-11-11 04:16:29

by Andrii Nakryiko

Subject: Re: [PATCH v2] bpf: Fix unsigned 'datasec_id' compared with zero in check_pseudo_btf_id

On Tue, Nov 10, 2020 at 6:59 PM <[email protected]> wrote:
>
> From: Kaixu Xia <[email protected]>
>
> 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 <[email protected]>
> Signed-off-by: Kaixu Xia <[email protected]>
> ---
> v2:
> -split out datasec_id definition into a separate line.
>
> kernel/bpf/verifier.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 6200519582a6..3fea4fc04e94 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -9572,7 +9572,8 @@ 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;
> + u32 type, id = insn->imm;
> const struct btf_var_secinfo *vsi;
> const struct btf_type *datasec;
> const struct btf_type *t;
> --
> 2.20.0
>

It would look a bit cleaner if you did it this way:

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 10da26e55130..f674b1403637 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -9585,12 +9585,13 @@ 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;
const struct btf_var_secinfo *vsi;
const struct btf_type *datasec;
const struct btf_type *t;
const char *sym_name;
bool percpu = false;
+ u32 type, id = insn->imm;
+ s32 datasec_id;
u64 addr;
int i;