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[PATCH bpf-next] libbpf: Remove redundant check in btf_ext__new()

Yuntao Wang posted 1 patch 4 years, 3 months ago 
tools/lib/bpf/btf.c | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)
[PATCH bpf-next] libbpf: Remove redundant check in btf_ext__new()
Posted by Yuntao Wang 4 years, 3 months ago 
Since 'core_relo_len' is the last field of 'struct btf_ext_header', if
'xxx->hdr_len' is not less than 'offsetofend(xxx, core_relo_len)', then
'xxx->hdr_len' must also be not less than 'offsetofend(xxx, line_info_len)'.

We can check 'xxx->hdr_len < offsetofend(xxx, core_relo_len)' first, if it
passes, the 'xxx->hdr_len < offsetofend(xxx, line_info_len)' check will be
redundant, it can be removed.

Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
---
 tools/lib/bpf/btf.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 1383e26c5d1f..d55b44124c3e 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -2813,7 +2813,7 @@ struct btf_ext *btf_ext__new(const __u8 *data, __u32 size)
 	if (err)
 		goto done;
 
-	if (btf_ext->hdr->hdr_len < offsetofend(struct btf_ext_header, line_info_len)) {
+	if (btf_ext->hdr->hdr_len < offsetofend(struct btf_ext_header, core_relo_len)) {
 		err = -EINVAL;
 		goto done;
 	}
@@ -2826,11 +2826,6 @@ struct btf_ext *btf_ext__new(const __u8 *data, __u32 size)
 	if (err)
 		goto done;
 
-	if (btf_ext->hdr->hdr_len < offsetofend(struct btf_ext_header, core_relo_len)) {
-		err = -EINVAL;
-		goto done;
-	}
-
 	err = btf_ext_setup_core_relos(btf_ext);
 	if (err)
 		goto done;
-- 
2.35.1
Re: [PATCH bpf-next] libbpf: Remove redundant check in btf_ext__new()
Posted by Andrii Nakryiko 4 years, 3 months ago 
On Sat, Mar 12, 2022 at 9:14 AM Yuntao Wang <ytcoode@gmail.com> wrote:
>
> Since 'core_relo_len' is the last field of 'struct btf_ext_header', if
> 'xxx->hdr_len' is not less than 'offsetofend(xxx, core_relo_len)', then
> 'xxx->hdr_len' must also be not less than 'offsetofend(xxx, line_info_len)'.
>
> We can check 'xxx->hdr_len < offsetofend(xxx, core_relo_len)' first, if it
> passes, the 'xxx->hdr_len < offsetofend(xxx, line_info_len)' check will be
> redundant, it can be removed.
>
> Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
> ---
>  tools/lib/bpf/btf.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
>
> diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
> index 1383e26c5d1f..d55b44124c3e 100644
> --- a/tools/lib/bpf/btf.c
> +++ b/tools/lib/bpf/btf.c
> @@ -2813,7 +2813,7 @@ struct btf_ext *btf_ext__new(const __u8 *data, __u32 size)
>         if (err)
>                 goto done;
>
> -       if (btf_ext->hdr->hdr_len < offsetofend(struct btf_ext_header, line_info_len)) {
> +       if (btf_ext->hdr->hdr_len < offsetofend(struct btf_ext_header, core_relo_len)) {
>                 err = -EINVAL;
>                 goto done;
>         }
> @@ -2826,11 +2826,6 @@ struct btf_ext *btf_ext__new(const __u8 *data, __u32 size)
>         if (err)
>                 goto done;
>
> -       if (btf_ext->hdr->hdr_len < offsetofend(struct btf_ext_header, core_relo_len)) {
> -               err = -EINVAL;
> -               goto done;
> -       }

it seems like it's actually a bug. If header is smaller then core
relos parsing should be skipped, I think. Maybe let's fix that
instead?

basically the logic should be:

1. if size of header is exactly == offsetof(core_relo_off) then skip core relos
2. otherwise check that it has enough size to cover core_relo_off and
core_relo_len, and error out if not
3. otherwise proceed to parsing core relos

> -
>         err = btf_ext_setup_core_relos(btf_ext);
>         if (err)
>                 goto done;
> --
> 2.35.1
>
[PATCH bpf-next v2] libbpf: Don't return -EINVAL if hdr_len < offsetofend(core_relo_len)
Posted by Yuntao Wang 4 years, 3 months ago 
Since core relos is an optional part of the .BTF.ext ELF section, we should
skip parsing it instead of returning -EINVAL if header size is less than
offsetofend(struct btf_ext_header, core_relo_len).

Fixes: e9fc3ce99b34 ("libbpf: Streamline error reporting for high-level APIs")
Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
---
v1 -> v2: skip core relos if hdr_len < offsetofend(core_relo_len)

 tools/lib/bpf/btf.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 1383e26c5d1f..9b7196b21498 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -2826,10 +2826,8 @@ struct btf_ext *btf_ext__new(const __u8 *data, __u32 size)
 	if (err)
 		goto done;
 
-	if (btf_ext->hdr->hdr_len < offsetofend(struct btf_ext_header, core_relo_len)) {
-		err = -EINVAL;
-		goto done;
-	}
+	if (btf_ext->hdr->hdr_len < offsetofend(struct btf_ext_header, core_relo_len))
+		goto done; // skip core relos parsing
 
 	err = btf_ext_setup_core_relos(btf_ext);
 	if (err)
-- 
2.35.1
Re: [PATCH bpf-next v2] libbpf: Don't return -EINVAL if hdr_len < offsetofend(core_relo_len)
Posted by Andrii Nakryiko 4 years, 2 months ago 
On Wed, Mar 16, 2022 at 7:52 AM Yuntao Wang <ytcoode@gmail.com> wrote:
>
> Since core relos is an optional part of the .BTF.ext ELF section, we should
> skip parsing it instead of returning -EINVAL if header size is less than
> offsetofend(struct btf_ext_header, core_relo_len).
>
> Fixes: e9fc3ce99b34 ("libbpf: Streamline error reporting for high-level APIs")
> Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
> ---
> v1 -> v2: skip core relos if hdr_len < offsetofend(core_relo_len)
>

Seems like this never made it to Patchworks. Can you please trim down
the CC list and resubmit?

>  tools/lib/bpf/btf.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
> index 1383e26c5d1f..9b7196b21498 100644
> --- a/tools/lib/bpf/btf.c
> +++ b/tools/lib/bpf/btf.c
> @@ -2826,10 +2826,8 @@ struct btf_ext *btf_ext__new(const __u8 *data, __u32 size)
>         if (err)
>                 goto done;
>
> -       if (btf_ext->hdr->hdr_len < offsetofend(struct btf_ext_header, core_relo_len)) {
> -               err = -EINVAL;
> -               goto done;
> -       }
> +       if (btf_ext->hdr->hdr_len < offsetofend(struct btf_ext_header, core_relo_len))
> +               goto done; // skip core relos parsing

don't use C++-style comments, only /* */

>
>         err = btf_ext_setup_core_relos(btf_ext);
>         if (err)
> --
> 2.35.1
>
[PATCH bpf-next v3] libbpf: Don't return -EINVAL if hdr_len < offsetofend(core_relo_len)
Posted by Yuntao Wang 4 years, 2 months ago 
Since core relos is an optional part of the .BTF.ext ELF section, we should
skip parsing it instead of returning -EINVAL if header size is less than
offsetofend(struct btf_ext_header, core_relo_len).

Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
---
v1 -> v2: skip core relos if hdr_len < offsetofend(core_relo_len)
v2 -> v3: fix comment style

 tools/lib/bpf/btf.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 1383e26c5d1f..d124e9e533f0 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -2826,10 +2826,8 @@ struct btf_ext *btf_ext__new(const __u8 *data, __u32 size)
 	if (err)
 		goto done;
 
-	if (btf_ext->hdr->hdr_len < offsetofend(struct btf_ext_header, core_relo_len)) {
-		err = -EINVAL;
-		goto done;
-	}
+	if (btf_ext->hdr->hdr_len < offsetofend(struct btf_ext_header, core_relo_len))
+		goto done; /* skip core relos parsing */
 
 	err = btf_ext_setup_core_relos(btf_ext);
 	if (err)
-- 
2.35.1
Re: [PATCH bpf-next v3] libbpf: Don't return -EINVAL if hdr_len < offsetofend(core_relo_len)
Posted by patchwork-bot+netdevbpf@kernel.org 4 years, 2 months ago 
Hello:

This patch was applied to bpf/bpf-next.git (master)
by Andrii Nakryiko <andrii@kernel.org>:

On Mon,  4 Apr 2022 08:53:20 +0800 you wrote:
> Since core relos is an optional part of the .BTF.ext ELF section, we should
> skip parsing it instead of returning -EINVAL if header size is less than
> offsetofend(struct btf_ext_header, core_relo_len).
> 
> Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
> ---
> v1 -> v2: skip core relos if hdr_len < offsetofend(core_relo_len)
> v2 -> v3: fix comment style
> 
> [...]

Here is the summary with links:
  - [bpf-next,v3] libbpf: Don't return -EINVAL if hdr_len < offsetofend(core_relo_len)
    https://git.kernel.org/bpf/bpf-next/c/a6a86da847eb

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