linux-kernel - Re: [PATCH v2 2/4] fprobe: make fprobe_kprobe

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Date:   Tue, 16 May 2023 17:51:34 +0800
From:   Ze Gao <zegao2021@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Albert Ou <aou@...s.berkeley.edu>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vasily Gorbik <gor@...ux.ibm.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-s390@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        bpf@...r.kernel.org, Conor Dooley <conor@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>, Yonghong Song <yhs@...com>,
        Ze Gao <zegao@...cent.com>
Subject: Re: [PATCH v2 2/4] fprobe: make fprobe_kprobe_handler recursion free

Sorry for paste the wrong link, it's this one instead:
  Link: https://lore.kernel.org/bpf/20230513001757.75ae0d1b@rorschach.local.home/

It's the original discussions of this problem.

Regards,
Ze

On Tue, May 16, 2023 at 5:47 PM Ze Gao <zegao2021@...il.com> wrote:
>
> Precisely, these that are called within kprobe_busy_{begin, end},
> which the previous patch does not resolve.
> I will refine the commit message to make it clear.
>
> FYI, details can checked out here:
>     Link: https://lore.kernel.org/linux-trace-kernel/20230516132516.c902edcf21028874a74fb868@kernel.org/
>
> Regards,
> Ze
>
> On Tue, May 16, 2023 at 5:18 PM Peter Zijlstra <peterz@...radead.org> wrote:
> >
> > On Tue, May 16, 2023 at 03:18:28PM +0800, Ze Gao wrote:
> > > Current implementation calls kprobe related functions before doing
> > > ftrace recursion check in fprobe_kprobe_handler, which opens door
> > > to kernel crash due to stack recursion if preempt_count_{add, sub}
> > > is traceable.
> >
> > Which preempt_count*() are you referring to? The ones you just made
> > _notrace in the previous patch?