If the length of the name string is 1 and the value of name[0] is NULL 
byte, an OOB vulnerability occurs in btf_name_valid_section() and the 
return value is true, so the invalid name passes the check. 

To solve this, you need to check if the first position is NULL byte.

Fixes: bd70a8fb7ca4 ("bpf: Allow all printable characters in BTF DATASEC names")
Signed-off-by: Jeongjun Park <aha310510@gmail.com>
---
 kernel/bpf/btf.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 520f49f422fe..5c24ea1a65a4 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -823,6 +823,9 @@ static bool btf_name_valid_section(const struct btf *btf, u32 offset)
 	const char *src = btf_str_by_offset(btf, offset);
 	const char *src_limit;
 
+	if (!*src)
+		return false;
+
 	/* set a limit on identifier length */
 	src_limit = src + KSYM_NAME_LEN;
 	src++;
--

On Fri, Aug 23, 2024 at 3:43 AM Jeongjun Park <aha310510@gmail.com> wrote:
>
> If the length of the name string is 1 and the value of name[0] is NULL
> byte, an OOB vulnerability occurs in btf_name_valid_section() and the
> return value is true, so the invalid name passes the check.
>
> To solve this, you need to check if the first position is NULL byte.
>
> Fixes: bd70a8fb7ca4 ("bpf: Allow all printable characters in BTF DATASEC names")
> Signed-off-by: Jeongjun Park <aha310510@gmail.com>
> ---
>  kernel/bpf/btf.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> index 520f49f422fe..5c24ea1a65a4 100644
> --- a/kernel/bpf/btf.c
> +++ b/kernel/bpf/btf.c
> @@ -823,6 +823,9 @@ static bool btf_name_valid_section(const struct btf *btf, u32 offset)
>         const char *src = btf_str_by_offset(btf, offset);
>         const char *src_limit;
>
> +       if (!*src)
> +               return false;
> +

We've talked about it. Quote:
"Pls add a selftest that demonstrates the issue
and produce a patch to fix just that."

length == 1 and name[0] = 0 is a hypothesis.
Demonstrate that such a scenario is possible then this patch will be
worth applying.

pw-bot: cr