[PATCH bpf] bpf: btf: Fix end boundary calculation for type section

[PATCH bpf] bpf: btf: Fix end boundary calculation for type section

[Martin KaFai Lau]

The end boundary math for type section is incorrect in
btf_check_all_metas().  It just happens that hdr->type_off
is always 0 for now because there are only two sections
(type and string) and string section must be at the end (ensured
in btf_parse_str_sec).

However, type_off may not be 0 if a new section would be added later.
This patch fixes it.

Fixes: f80442a4cd18 ("bpf: btf: Change how section is supported in btf_header")
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
---
 kernel/bpf/btf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 2590700237c1..138f0302692e 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -1844,7 +1844,7 @@ static int btf_check_all_metas(struct btf_verifier_env *env)
 
 	hdr = &btf->hdr;
 	cur = btf->nohdr_data + hdr->type_off;
-	end = btf->nohdr_data + hdr->type_len;
+	end = cur + hdr->type_len;
 
 	env->log_type_id = 1;
 	while (cur < end) {
-- 
2.17.1

Re: [PATCH bpf] bpf: btf: Fix end boundary calculation for type section

[Yonghong Song]

On 9/12/18 10:29 AM, Martin KaFai Lau wrote:
> The end boundary math for type section is incorrect in
> btf_check_all_metas().  It just happens that hdr->type_off
> is always 0 for now because there are only two sections
> (type and string) and string section must be at the end (ensured
> in btf_parse_str_sec).
> 
> However, type_off may not be 0 if a new section would be added later.
> This patch fixes it.
> 
> Fixes: f80442a4cd18 ("bpf: btf: Change how section is supported in btf_header")
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Signed-off-by: Martin KaFai Lau <kafai@fb.com>

Acked-by: Yonghong Song <yhs@fb.com>

> ---
>   kernel/bpf/btf.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> index 2590700237c1..138f0302692e 100644
> --- a/kernel/bpf/btf.c
> +++ b/kernel/bpf/btf.c
> @@ -1844,7 +1844,7 @@ static int btf_check_all_metas(struct btf_verifier_env *env)
>   
>   	hdr = &btf->hdr;
>   	cur = btf->nohdr_data + hdr->type_off;
> -	end = btf->nohdr_data + hdr->type_len;
> +	end = cur + hdr->type_len;
>   
>   	env->log_type_id = 1;
>   	while (cur < end) {
> 

Re: [PATCH bpf] bpf: btf: Fix end boundary calculation for type section

[Daniel Borkmann]

On 09/12/2018 07:29 PM, Martin KaFai Lau wrote:
> The end boundary math for type section is incorrect in
> btf_check_all_metas().  It just happens that hdr->type_off
> is always 0 for now because there are only two sections
> (type and string) and string section must be at the end (ensured
> in btf_parse_str_sec).
> 
> However, type_off may not be 0 if a new section would be added later.
> This patch fixes it.
> 
> Fixes: f80442a4cd18 ("bpf: btf: Change how section is supported in btf_header")
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Signed-off-by: Martin KaFai Lau <kafai@fb.com>

Applied to bpf, thanks everyone!