On Mon, 16 Mar 2015 16:27:47 +0100 Petr Mladek <[email protected]> wrote:
> arm_kprobe_ftrace() could fail, especially after introducing ftrace IPMODIFY > flag and LifePatching. But this situation is not properly handled. > This patch adds the most important changes. > > First, it does not make sense to register "kprobe_ftrace_ops" if the filter > was > not set. > > Second, we should remove the filter if the registration of "kprobe_ftrace_ops" > fails. The failure might be caused by conflict between the Kprobe and > a life patch via the IPMODIFY flag. If we remove the filter, we will allow > to register "kprobe_ftrace_ops" for another non-conflicting Kprobe later. > > Third, we need to make sure that "kprobe_ftrace_enabled" is incremented only > when "kprobe_ftrace_ops" is successfully registered. Otherwise, another > Kprobe will not try to register it again. Note that we could move the > manipulation with this counter because it is accessed only under > "kprobe_mutex". > > Four, we should mark the probe as disabled if the ftrace stuff is not usable. > It will be the correct status. Also it will prevent the unregistration code > from producing another failure. > > It looks more safe to disable the Kprobe directly in "kprobe_ftrace_ops". Note > that we need to disable also all listed Kprobes in case of an aggregated > probe. > It would be enough to disable only the new one but we do not know which one it > was. They should be in sync anyway. > I can pull this into my tree. But there's one little nit below. > Signed-off-by: Petr Mladek <[email protected]> > Acked-by: Masami Hiramatsu <[email protected]> > --- > Hi, > > I resend this patch separately and have just added the acked by Masami. > > Best Regards, > Petr > > kernel/kprobes.c | 25 +++++++++++++++++++++---- > 1 file changed, 21 insertions(+), 4 deletions(-) > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > index c90e417bb963..54b22db084f3 100644 > --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -932,16 +932,33 @@ static int prepare_kprobe(struct kprobe *p) > /* Caller must lock kprobe_mutex */ > static void arm_kprobe_ftrace(struct kprobe *p) > { > + struct kprobe *kp; > int ret; > > ret = ftrace_set_filter_ip(&kprobe_ftrace_ops, > (unsigned long)p->addr, 0, 0); > - WARN(ret < 0, "Failed to arm kprobe-ftrace at %p (%d)\n", p->addr, ret); > - kprobe_ftrace_enabled++; > - if (kprobe_ftrace_enabled == 1) { > + if (WARN(ret < 0, > + "Failed to arm kprobe-ftrace at %p (%d). The kprobe gets > disabled.\n", > + p->addr, ret)) > + goto err_filter; > + > + if (!kprobe_ftrace_enabled) { > ret = register_ftrace_function(&kprobe_ftrace_ops); > - WARN(ret < 0, "Failed to init kprobe-ftrace (%d)\n", ret); > + if (WARN(ret < 0, > + "Failed to init kprobe-ftrace (%d). The probe at %p > gets disabled\n", > + ret, p->addr)) > + goto err_function; > } > + kprobe_ftrace_enabled++; > + return; > + > +err_function: > + ftrace_set_filter_ip(&kprobe_ftrace_ops, (unsigned long)p->addr, 1, 0); > +err_filter: > + p->flags |= KPROBE_FLAG_DISABLED; > + if (kprobe_aggrprobe(p)) > + list_for_each_entry_rcu(kp, &p->list, list) > + kp->flags |= KPROBE_FLAG_DISABLED; The if statement should have brackets. No bracket if and for statements should only be used when there's a singe simple non complex line below. This is not the case. Thanks, -- Steve > } > > /* Caller must lock kprobe_mutex */ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
