linux-kernel - Re: [PATCH bpf] bpf: add check for invalid name in btf_name_valid

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Message-ID: <3a48e38f29cc8c73e36a6d3339b9303571d522a8.camel@gmail.com>
Date: Thu, 29 Aug 2024 18:26:00 -0700
From: Eduard Zingerman <eddyz87@...il.com>
To: Jeongjun Park <aha310510@...il.com>, alexei.starovoitov@...il.com
Cc: andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org,
 daniel@...earbox.net,  haoluo@...gle.com, john.fastabend@...il.com,
 jolsa@...nel.org, kpsingh@...nel.org,  linux-kernel@...r.kernel.org,
 martin.lau@...ux.dev, sdf@...ichev.me,  song@...nel.org,
 yonghong.song@...ux.dev
Subject: Re: [PATCH bpf] bpf: add check for invalid name in
 btf_name_valid_section()

On Wed, 2024-08-28 at 22:45 -0700, Eduard Zingerman wrote:

[...]

> I will prepare a test case.
> Probably tomorrow.

Please find test in the attachment. This test triggers KASAN error
report as in another attachment. (I enabled CONFIG_KASAN using
menuconfig on top of regular selftest config).

On Fri, Aug 23, 2024 at 3:43 AM Jeongjun Park <aha310510@...il.com> wrote:

[...]

> 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;
> +

I think that correct fix would be as follows:

---

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index edad152cee8e..d583d76fcace 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -820,7 +820,6 @@ 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;


View attachment "bad-name-test.patch" of type "text/x-patch" (899 bytes)

View attachment "bad-name-kasan-report.txt" of type "text/plain" (4997 bytes)