Re: [PATCH bpf-next] bpf: fix oob in btf_name_valid_section

[Eduard Zingerman <eddyz87@gmail.com>]

On Mon, 2024-03-11 at 21:16 +0800, Edward Adam Davis wrote:
> Check the first char of the BTF DATASEC names.
> 
> Fixes: bd70a8fb7ca4 ("bpf: Allow all printable characters in BTF DATASEC names")
> Reported-and-tested-by: syzbot+cc32304f6487ebff9b70@syzkaller.appspotmail.com
> Signed-off-by: Edward Adam Davis <eadavis@qq.com>
> ---
>  kernel/bpf/btf.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> index 170d017e8e4a..dda0aa0d7175 100644
> --- a/kernel/bpf/btf.c
> +++ b/kernel/bpf/btf.c
> @@ -816,6 +816,8 @@ 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 (!isprint(*src))
> +		return false;
>  	/* set a limit on identifier length */
>  	src_limit = src + KSYM_NAME_LEN;
>  	src++;

Hi Edward,

Thank you for fixing this.
I wonder, maybe something like below would be simpler?

Thanks,
Eduard

---

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 170d017e8e4a..3d95d5398c8a 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -818,7 +818,6 @@ static bool btf_name_valid_section(const struct btf *btf, u32 offset)
 
        /* set a limit on identifier length */
        src_limit = src + KSYM_NAME_LEN;
-       src++;
        while (*src && src < src_limit) {
                if (!isprint(*src))
                        return false;