From: He Fengqing <hefengqing@huawei.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Song Liu <song@kernel.org>, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
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@kernel.org>,
"David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [bpf-next 3/3] bpf: Fix a use after free in bpf_check()
Date: Fri, 9 Jul 2021 19:11:25 +0800 [thread overview]
Message-ID: <bc75c9c5-7479-5021-58ea-ed8cf53fb331@huawei.com> (raw)
In-Reply-To: <CAADnVQJ0Q0dLVs5UM-CyJe90N+KHomccAy-S_LOOARa9nXkXsA@mail.gmail.com>
在 2021/7/8 11:09, Alexei Starovoitov 写道:
> On Wed, Jul 7, 2021 at 8:00 PM He Fengqing <hefengqing@huawei.com> wrote:
>>
>> Ok, I will change this in next version.
>
> before you spam the list with the next version
> please explain why any of these changes are needed?
> I don't see an explanation in the patches and I don't see a bug in the code.
> Did you check what is the prog clone ?
> When is it constructed? Why verifier has anything to do with it?
> .
>
I'm sorry, I didn't describe these errors clearly.
bpf_check(bpf_verifier_env)
|
|->do_misc_fixups(env)
| |
| |->bpf_patch_insn_data(env)
| | |
| | |->bpf_patch_insn_single(env->prog)
| | | |
| | | |->bpf_prog_realloc(env->prog)
| | | | |
| | | | |->construct new_prog
| | | | | free old_prog(env->prog)
| | | | |
| | | | |->return new_prog;
| | | |
| | | |->return new_prog;
| | |
| | |->adjust_insn_aux_data
| | | |
| | | |->return ENOMEM;
| | |
| | |->return NULL;
| |
| |->return ENOMEM;
bpf_verifier_env->prog had been freed in bpf_prog_realloc function.
There are two errors here, the first is memleak in the
bpf_patch_insn_data function, and the second is use after free in the
bpf_check function.
memleak in bpf_patch_insn_data:
Look at the call chain above, if adjust_insn_aux_data function return
ENOMEM, bpf_patch_insn_data will return NULL, but we do not free the
new_prog.
So in the patch 2, before bpf_patch_insn_data return NULL, we free the
new_prog.
use after free in bpf_check:
If bpf_patch_insn_data function return NULL, we will not assign new_prog
to the bpf_verifier_env->prog, but bpf_verifier_env->prog has been freed
in the bpf_prog_realloc function. Then in bpf_check function, we will
use bpf_verifier_env->prog after do_misc_fixups function.
In the patch 3, I added a free_old parameter to bpf_prog_realloc, in
this scenario we don't free old_prog. Instead, we free it in the
do_misc_fixups function when bpf_patch_insn_data return a valid new_prog.
Thanks for your reviews.
next prev parent reply other threads:[~2021-07-09 11:11 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-07 4:38 [bpf-next 0/3] potential memleak and use after free in bpf verifier He Fengqing
2021-07-07 4:38 ` [bpf-next 1/3] bpf: Move bpf_prog_clone_free into filter.h file He Fengqing
2021-07-07 7:02 ` Song Liu
2021-07-07 4:38 ` [bpf-next 2/3] bpf: Fix a memory leak in an error handling path in 'bpf_patch_insn_data()' He Fengqing
2021-07-07 4:38 ` [bpf-next 3/3] bpf: Fix a use after free in bpf_check() He Fengqing
2021-07-07 7:25 ` Song Liu
2021-07-08 3:00 ` He Fengqing
2021-07-08 3:09 ` Alexei Starovoitov
2021-07-09 11:11 ` He Fengqing [this message]
2021-07-09 15:12 ` Alexei Starovoitov
2021-07-12 2:17 ` He Fengqing
2021-07-13 23:17 ` Alexei Starovoitov
2021-07-14 1:53 ` He Fengqing
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=bc75c9c5-7479-5021-58ea-ed8cf53fb331@huawei.com \
--to=hefengqing@huawei.com \
--cc=alexei.starovoitov@gmail.com \
--cc=andrii@kernel.org \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=davem@davemloft.net \
--cc=john.fastabend@gmail.com \
--cc=kafai@fb.com \
--cc=kpsingh@kernel.org \
--cc=kuba@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=song@kernel.org \
--cc=songliubraving@fb.com \
--cc=yhs@fb.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).