From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
To: Jiri Olsa <olsajiri@gmail.com>
Cc: Ze Gao <zegao2021@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Albert Ou <aou@eecs.berkeley.edu>,
Alexander Gordeev <agordeev@linux.ibm.com>,
Alexei Starovoitov <ast@kernel.org>,
Borislav Petkov <bp@alien8.de>,
Christian Borntraeger <borntraeger@linux.ibm.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Heiko Carstens <hca@linux.ibm.com>,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Sven Schnelle <svens@linux.ibm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Vasily Gorbik <gor@linux.ibm.com>,
x86@kernel.org, bpf@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org,
linux-s390@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
Conor Dooley <conor@kernel.org>, Yonghong Song <yhs@fb.com>,
Ze Gao <zegao@tencent.com>
Subject: Re: [PATCH v3 2/4] fprobe: make fprobe_kprobe_handler recursion free
Date: Wed, 17 May 2023 20:42:36 +0900 [thread overview]
Message-ID: <20230517204236.e0f579399e5a69505a4ec7ef@kernel.org> (raw)
In-Reply-To: <ZGSwzuM8oHgKaaga@krava>
On Wed, 17 May 2023 12:47:42 +0200
Jiri Olsa <olsajiri@gmail.com> wrote:
> On Wed, May 17, 2023 at 11:45:07AM +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 in kprobe_busy_{begin, end}.
> >
> > Things goes like this without this patch quoted from Steven:
> > "
> > fprobe_kprobe_handler() {
> > kprobe_busy_begin() {
> > preempt_disable() {
> > preempt_count_add() { <-- trace
> > fprobe_kprobe_handler() {
> > [ wash, rinse, repeat, CRASH!!! ]
> > "
> >
> > By refactoring the common part out of fprobe_kprobe_handler and
> > fprobe_handler and call ftrace recursion detection at the very beginning,
> > the whole fprobe_kprobe_handler is free from recursion.
> >
> > Signed-off-by: Ze Gao <zegao@tencent.com>
> > Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> > Link: https://lore.kernel.org/linux-trace-kernel/20230516071830.8190-3-zegao@tencent.com
> > ---
> > kernel/trace/fprobe.c | 59 ++++++++++++++++++++++++++++++++-----------
> > 1 file changed, 44 insertions(+), 15 deletions(-)
> >
> > diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
> > index 9abb3905bc8e..097c740799ba 100644
> > --- a/kernel/trace/fprobe.c
> > +++ b/kernel/trace/fprobe.c
> > @@ -20,30 +20,22 @@ struct fprobe_rethook_node {
> > char data[];
> > };
> >
> > -static void fprobe_handler(unsigned long ip, unsigned long parent_ip,
> > - struct ftrace_ops *ops, struct ftrace_regs *fregs)
> > +static inline void __fprobe_handler(unsigned long ip, unsigned long
> > + parent_ip, struct ftrace_ops *ops, struct ftrace_regs *fregs)
> > {
> > struct fprobe_rethook_node *fpr;
> > struct rethook_node *rh = NULL;
> > struct fprobe *fp;
> > void *entry_data = NULL;
> > - int bit, ret;
> > + int ret;
> >
>
> this change uncovered bug for me introduced by [1]
>
> the bpf's kprobe multi uses either fprobe's entry_handler or exit_handler,
> so the 'ret' value is undefined for return probe path and occasionally we
> won't setup rethook and miss the return probe
Oops, I missed to push my fix.
https://lore.kernel.org/all/168100731160.79534.374827110083836722.stgit@devnote2/
>
> we can either squash this change into your patch or I can make separate
> patch for that.. but given that [1] is quite recent we could just silently
> fix that ;-)
Jiri, I think the above will fix the issue, right?
>
> jirka
>
>
> [1] 39d954200bf6 fprobe: Skip exit_handler if entry_handler returns !0
>
> ---
> diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
> index 9abb3905bc8e..293184227394 100644
> --- a/kernel/trace/fprobe.c
> +++ b/kernel/trace/fprobe.c
> @@ -27,7 +27,7 @@ static void fprobe_handler(unsigned long ip, unsigned long parent_ip,
> struct rethook_node *rh = NULL;
> struct fprobe *fp;
> void *entry_data = NULL;
> - int bit, ret;
> + int bit, ret = 0;
>
> fp = container_of(ops, struct fprobe, ops);
> if (fprobe_disabled(fp))
>
>
--
Masami Hiramatsu (Google) <mhiramat@kernel.org>
next prev parent reply other threads:[~2023-05-17 11:42 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-17 3:45 [PATCH v3 0/3] Make fprobe + rethook immune to recursion Ze Gao
2023-05-17 3:45 ` [PATCH v3 1/4] rethook: use preempt_{disable, enable}_notrace in rethook_trampoline_handler Ze Gao
2023-05-17 11:59 ` Masami Hiramatsu
2023-05-18 2:40 ` Ze Gao
2023-05-17 3:45 ` [PATCH v3 2/4] fprobe: make fprobe_kprobe_handler recursion free Ze Gao
2023-05-17 10:47 ` Jiri Olsa
2023-05-17 11:42 ` Masami Hiramatsu [this message]
2023-05-17 12:30 ` Jiri Olsa
2023-05-17 14:27 ` Masami Hiramatsu
2023-05-18 0:16 ` Andrii Nakryiko
2023-05-18 2:49 ` Ze Gao
2023-06-28 7:16 ` Yafang Shao
2023-07-03 6:52 ` Ze Gao
2023-05-17 3:45 ` [PATCH v3 3/4] fprobe: add recursion detection in fprobe_exit_handler Ze Gao
2023-05-17 3:45 ` [PATCH v3 4/4] rethook, fprobe: do not trace rethook related functions Ze Gao
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