From: Daniel Borkmann <daniel@iogearbox.net>
To: Dongliang Mu <dzm91@hust.edu.cn>,
Alexei Starovoitov <ast@kernel.org>,
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>
Cc: Dongliang Mu <mudongliangabcd@gmail.com>,
syzkaller <syzkaller@googlegroups.com>,
netdev@vger.kernel.org, bpf@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] bpf: cgroup: remove WARN_ON at bpf_cgroup_link_release
Date: Tue, 1 Mar 2022 17:28:19 +0100 [thread overview]
Message-ID: <d4bed569-d448-8b59-0774-c036e4c9abe9@iogearbox.net> (raw)
In-Reply-To: <20220227134009.1298488-1-dzm91@hust.edu.cn>
On 2/27/22 2:40 PM, Dongliang Mu wrote:
> From: Dongliang Mu <mudongliangabcd@gmail.com>
>
> When syzkaller injects fault into memory allocation at
> bpf_prog_array_alloc, the kernel encounters a memory failure and
> returns non-zero, thus leading to one WARN_ON at
> bpf_cgroup_link_release. The stack trace is as follows:
>
> __kmalloc+0x7e/0x3d0
> bpf_prog_array_alloc+0x4f/0x60
> compute_effective_progs+0x132/0x580
> ? __sanitizer_cov_trace_pc+0x1a/0x40
> update_effective_progs+0x5e/0x260
> __cgroup_bpf_detach+0x293/0x760
> bpf_cgroup_link_release+0xad/0x400
> bpf_link_free+0xca/0x190
> bpf_link_put+0x161/0x1b0
> bpf_link_release+0x33/0x40
> __fput+0x286/0x9f0
>
> Fix this by removing the WARN_ON for __cgroup_bpf_detach.
>
> Reported-by: syzkaller <syzkaller@googlegroups.com>
> Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com>
> ---
> kernel/bpf/cgroup.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
> index 514b4681a90a..fdbdcee6c9fa 100644
> --- a/kernel/bpf/cgroup.c
> +++ b/kernel/bpf/cgroup.c
> @@ -896,8 +896,8 @@ static void bpf_cgroup_link_release(struct bpf_link *link)
> return;
> }
>
> - WARN_ON(__cgroup_bpf_detach(cg_link->cgroup, NULL, cg_link,
> - cg_link->type));
> + __cgroup_bpf_detach(cg_link->cgroup, NULL, cg_link,
> + cg_link->type);
"Fixing" by removing WARN_ON is just papering over the issue which in this case as
mentioned is allocation failure on detach/teardown when allocating and recomputing
effective prog arrays..
> cg = cg_link->cgroup;
> cg_link->cgroup = NULL;
>
next prev parent reply other threads:[~2022-03-01 16:28 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-27 13:40 [PATCH] bpf: cgroup: remove WARN_ON at bpf_cgroup_link_release Dongliang Mu
2022-03-01 16:28 ` Daniel Borkmann [this message]
2022-03-02 5:46 ` Dongliang Mu
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