From: Daniel Borkmann <daniel@iogearbox.net>
To: Peilin Ye <yepeilin.cs@gmail.com>,
Andrii Nakryiko <andriin@fb.com>,
Alexei Starovoitov <ast@kernel.org>
Cc: Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@chromium.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
netdev@vger.kernel.org, bpf@vger.kernel.org,
syzkaller-bugs@googlegroups.com,
linux-kernel-mentees@lists.linuxfoundation.org,
linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com
Subject: Re: [Linux-kernel-mentees] [PATCH v3] bpf: Fix NULL pointer dereference in __btf_resolve_helper_id()
Date: Wed, 15 Jul 2020 23:07:17 +0200 [thread overview]
Message-ID: <3b97c5bf-9f07-0353-ea4d-f90574fbcdc0@iogearbox.net> (raw)
In-Reply-To: <20200714180904.277512-1-yepeilin.cs@gmail.com>
On 7/14/20 8:09 PM, Peilin Ye wrote:
> Prevent __btf_resolve_helper_id() from dereferencing `btf_vmlinux`
> as NULL. This patch fixes the following syzbot bug:
>
> https://syzkaller.appspot.com/bug?id=f823224ada908fa5c207902a5a62065e53ca0fcc
>
> Reported-by: syzbot+ee09bda7017345f1fbe6@syzkaller.appspotmail.com
> Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
Looks good, applied, thanks! As far as I can tell all the other occurrences are
gated behind btf_parse_vmlinux() where we also init struct_opts, etc.
So for bpf-next this would then end up looking like ...
int btf_resolve_helper_id(struct bpf_verifier_log *log,
const struct bpf_func_proto *fn, int arg)
{
int id;
if (fn->arg_type[arg] != ARG_PTR_TO_BTF_ID)
return -EINVAL;
id = fn->btf_id[arg];
if (!id || !btf_vmlinux || id > btf_vmlinux->nr_types)
return -EINVAL;
return id;
}
> ---
> Sorry, I got the link wrong. Thank you for pointing that out.
>
> Change in v3:
> - Fix incorrect syzbot dashboard link.
>
> Change in v2:
> - Split NULL and IS_ERR cases.
>
> kernel/bpf/btf.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> index 30721f2c2d10..092116a311f4 100644
> --- a/kernel/bpf/btf.c
> +++ b/kernel/bpf/btf.c
> @@ -4088,6 +4088,11 @@ static int __btf_resolve_helper_id(struct bpf_verifier_log *log, void *fn,
> const char *tname, *sym;
> u32 btf_id, i;
>
> + if (!btf_vmlinux) {
> + bpf_log(log, "btf_vmlinux doesn't exist\n");
> + return -EINVAL;
> + }
> +
> if (IS_ERR(btf_vmlinux)) {
> bpf_log(log, "btf_vmlinux is malformed\n");
> return -EINVAL;
>
prev parent reply other threads:[~2020-07-15 21:07 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-14 0:38 [Linux-kernel-mentees] [PATCH] bpf: Fix NULL pointer dereference in __btf_resolve_helper_id() Peilin Ye
2020-07-14 0:53 ` Andrii Nakryiko
2020-07-14 1:27 ` [Linux-kernel-mentees] [PATCH v2] " Peilin Ye
2020-07-14 4:37 ` Andrii Nakryiko
2020-07-14 17:27 ` Alexei Starovoitov
2020-07-14 18:09 ` [Linux-kernel-mentees] [PATCH v3] " Peilin Ye
2020-07-15 21:07 ` Daniel Borkmann [this message]
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