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    SubjectRe: [PATCH] kretprobe: avoid re-registration of the same kretprobe earlier
    On Wed, 2 Dec 2020 09:23:35 +0800
    "Wangshaobo (bobo)" <bobo.shaobowang@huawei.com> wrote:

    > Hi steve, Masami,
    >
    > Thanks for your works, i will check code again and modify properly
    > according to steve's suggestion.
    >
    > -- ShaoBo
    >

    Anything happen with this?

    -- Steve


    > 在 2020/12/2 7:32, Masami Hiramatsu 写道:
    > > On Mon, 30 Nov 2020 16:18:50 -0500
    > > Steven Rostedt <rostedt@goodmis.org> wrote:
    > >
    > >> Masami,
    > >>
    > >> Can you review this patch, and also, should this go to -rc and stable?
    > >>
    > >> -- Steve
    > > Thanks for ping me!
    > >
    > >> On Tue, 24 Nov 2020 19:57:19 +0800
    > >> Wang ShaoBo <bobo.shaobowang@huawei.com> wrote:
    > >>
    > >>> Our system encountered a re-init error when re-registering same kretprobe,
    > >>> where the kretprobe_instance in rp->free_instances is illegally accessed
    > >>> after re-init.
    > > Ah, OK. Anyway if re-register happens on kretprobe, it must lose instances
    > > on the list before checking re-register in register_kprobe().
    > > So the idea looks good to me.
    > >
    > >
    > >>> Implementation to avoid re-registration has been introduced for kprobe
    > >>> before, but lags for register_kretprobe(). We must check if kprobe has
    > >>> been re-registered before re-initializing kretprobe, otherwise it will
    > >>> destroy the data struct of kretprobe registered, which can lead to memory
    > >>> leak, system crash, also some unexpected behaviors.
    > >>>
    > >>> we use check_kprobe_rereg() to check if kprobe has been re-registered
    > >>> before calling register_kretprobe(), for giving a warning message and
    > >>> terminate registration process.
    > >>>
    > >>> Signed-off-by: Wang ShaoBo <bobo.shaobowang@huawei.com>
    > >>> Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>
    > >>> ---
    > >>> kernel/kprobes.c | 8 ++++++++
    > >>> 1 file changed, 8 insertions(+)
    > >>>
    > >>> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
    > >>> index 41fdbb7953c6..7f54a70136f3 100644
    > >>> --- a/kernel/kprobes.c
    > >>> +++ b/kernel/kprobes.c
    > >>> @@ -2117,6 +2117,14 @@ int register_kretprobe(struct kretprobe *rp)
    > >>> }
    > >>> }
    > >>>
    > >>> + /*
    > >>> + * Return error if it's being re-registered,
    > >>> + * also give a warning message to the developer.
    > >>> + */
    > >>> + ret = check_kprobe_rereg(&rp->kp);
    > >>> + if (WARN_ON(ret))
    > >>> + return ret;
    > > If you call this here, you must make sure kprobe_addr() is called on rp->kp.
    > > But if kretprobe_blacklist_size == 0, kprobe_addr() is not called before
    > > this check. So it should be in between kprobe_on_func_entry() and
    > > kretprobe_blacklist_size check, like this
    > >
    > > if (!kprobe_on_func_entry(rp->kp.addr, rp->kp.symbol_name, rp->kp.offset))
    > > return -EINVAL;
    > >
    > > addr = kprobe_addr(&rp->kp);
    > > if (IS_ERR(addr))
    > > return PTR_ERR(addr);
    > > rp->kp.addr = addr;
    > >
    > > ret = check_kprobe_rereg(&rp->kp);
    > > if (WARN_ON(ret))
    > > return ret;
    > >
    > > if (kretprobe_blacklist_size) {
    > > for (i = 0; > > + ret = check_kprobe_rereg(&rp->kp);
    > >
    > >
    > > Thank you,
    > >
    > >

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