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[2001:1ae9:1c2:4c00:726e:c10f:8833:ff22]) by smtp.gmail.com with ESMTPSA id u9-20020a1709061da900b0079800b81709sm5470994ejh.219.2022.11.02.07.28.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Nov 2022 07:28:50 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Wed, 2 Nov 2022 15:28:47 +0100 To: Hao Sun Cc: Jiri Olsa , Linux Kernel Mailing List , andrii@kernel.org, ast@kernel.org, bpf , daniel@iogearbox.net, haoluo@google.com, john.fastabend@gmail.com, kpsingh@kernel.org, martin.lau@linux.dev, sdf@google.com, song@kernel.org, yhs@fb.com Subject: Re: WARNING in bpf_bprintf_prepare Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Thu, Oct 27, 2022 at 07:45:16PM +0800, Hao Sun wrote: > Jiri Olsa 于2022年10月27日周四 19:24写道： > > > > On Thu, Oct 27, 2022 at 10:27:28AM +0800, Hao Sun wrote: > > > Hi, > > > > > > The following warning can be triggered with the C reproducer in the link. > > > Syzbot also reported this several days ago, Jiri posted a patch that > > > uses bpf prog `active` field to fix this by 05b24ff9b2cfab (bpf: > > > Prevent bpf program recursion...) according to syzbot dashboard > > > (https://syzkaller.appspot.com/bug?id=179313fb375161d50a98311a28b8e2fc5f7350f9). > > > But this warning can still be triggered on 247f34f7b803 > > > (Linux-v6.1-rc2) that already merged the patch, so it seems that this > > > still is an issue. > > > > > > HEAD commit: 247f34f7b803 Linux 6.1-rc2 > > > git tree: upstream > > > console output: https://pastebin.com/raw/kNw8JCu5 > > > kernel config: https://pastebin.com/raw/sE5QK5HL > > > C reproducer: https://pastebin.com/raw/X96ASi27 > > > > hi, > > right, that fix addressed that issue for single bpf program, > > and it won't prevent if there are multiple programs hook on > > contention_begin tracepoint and calling bpf_trace_printk, > > > > I'm not sure we can do something there.. will check > > > > do you run just the reproducer, or you load the server somehow? > > I cannot hit the issue so far > > > > Hi, > > Last email has format issues, resend it here. > > I built the kernel with the config in the link, which contains > “CONFIG_CMDLINE="earlyprintk=serial net.ifnames=0 > sysctl.kernel.hung_task_all_cpu_backtrace=1 panic_on_warn=1 …”, and > boot the kernel with normal qemu setup and then the warning can be > triggered by executing the reproducer. > > Also, I’m willing to test the proposed patch if any. fyi I reproduced that.. will check if we can do anything about that thanks, jirka