From: John Fastabend <john.fastabend@gmail.com>
To: Jakub Sitnicki <jakub@cloudflare.com>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Edward Adam Davis <eadavis@qq.com>,
John Fastabend <john.fastabend@gmail.com>
Cc: syzbot+c4f4d25859c2e5859988@syzkaller.appspotmail.com,
42.hyeyoo@gmail.com, andrii@kernel.org, ast@kernel.org,
bpf@vger.kernel.org, daniel@iogearbox.net,
davem@davemloft.net, edumazet@google.com, kafai@fb.com,
kpsingh@kernel.org, kuba@kernel.org,
linux-kernel@vger.kernel.org, namhyung@kernel.org,
netdev@vger.kernel.org, pabeni@redhat.com,
peterz@infradead.org, songliubraving@fb.com,
syzkaller-bugs@googlegroups.com, yhs@fb.com
Subject: Re: [PATCH] bpf, sockmap: fix deadlock in rcu_report_exp_cpu_mult
Date: Thu, 28 Mar 2024 22:29:36 -0700 [thread overview]
Message-ID: <660651c0707f5_22b5520880@john.notmuch> (raw)
In-Reply-To: <87ttkuber7.fsf@cloudflare.com>
Jakub Sitnicki wrote:
> On Mon, Mar 25, 2024 at 01:23 PM +01, Jakub Sitnicki wrote:
>
> [...]
>
> > But we also need to cover sock_map_unref->sock_sock_map_del_link called
> > from sock_hash_delete_elem. It also grabs a spin lock.
>
> On second look, no need to disable interrupts in
> sock_map_unref->sock_sock_map_del_link. Call is enclosed in the critical
> section in sock_hash_delete_elem that has been updated.
>
> I have a question, though, why are we patching sock_hash_free? It
> doesn't get called unless there are no more existing users of the BPF
> map. So nothing can mutate it from interrupt context.
>
> [...]
Agree sock_hash_free should be only after all refs are dropped.
Edward, did you want to send a v2 for this? Also if you want fixing the
sockmap case as well would be useful. Also happy to finish up the patches
if you would rather not.
Thanks,
John
next prev parent reply other threads:[~2024-03-29 5:29 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-18 10:07 [syzbot] [bpf?] [net?] possible deadlock in rcu_report_exp_cpu_mult syzbot
2024-03-23 5:42 ` [PATCH] bpf, sockmap: fix " Edward Adam Davis
2024-03-23 7:08 ` Alexei Starovoitov
2024-03-25 12:23 ` Jakub Sitnicki
2024-03-25 13:49 ` Jakub Sitnicki
2024-03-29 5:29 ` John Fastabend [this message]
2024-03-26 22:15 ` Jakub Sitnicki
2024-03-29 15:52 ` Shung-Hsi Yu
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