2018-07-25 10:29:51

by Artem Savkov

Subject: [PATCH] kprobes: fix trace_probe flags in enable_trace_kprobe

If enable_trace_kprobe fails to enable the probe in enable_k(ret)probe
it returns an error, but does not unset the tp flags it set previosly.
This results in a probe being considered enabled and failures like being
unable to remove the probe through kprobe_events file since probes_open()
expects every probe to be disabled.

Signed-off-by: Artem Savkov <[email protected]>
---
kernel/trace/trace_kprobe.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 21f718472942..fb887ced5056 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -400,11 +400,10 @@ static struct trace_kprobe *find_trace_kprobe(const char *event,
static int
enable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file)
{
+ struct event_file_link *link;
int ret = 0;

if (file) {
- struct event_file_link *link;
-
link = kmalloc(sizeof(*link), GFP_KERNEL);
if (!link) {
ret = -ENOMEM;
@@ -424,6 +423,16 @@ enable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file)
else
ret = enable_kprobe(&tk->rp.kp);
}
+
+ if (ret) {
+ if (file) {
+ list_del(&link->list);
+ kfree(link);
+ tk->tp.flags &= ~TP_FLAG_TRACE;
+ } else {
+ tk->tp.flags &= ~TP_FLAG_PROFILE;
+ }
+ }
out:
return ret;
}
--
2.13.6

2018-07-25 13:23:47

by Steven Rostedt

Subject: Re: [PATCH] kprobes: fix trace_probe flags in enable_trace_kprobe

[ Adding Masami to Cc ]

On Wed, 25 Jul 2018 12:28:26 +0200
Artem Savkov <[email protected]> wrote:

> If enable_trace_kprobe fails to enable the probe in enable_k(ret)probe
> it returns an error, but does not unset the tp flags it set previosly.
> This results in a probe being considered enabled and failures like being
> unable to remove the probe through kprobe_events file since probes_open()
> expects every probe to be disabled.
>

Looks good to me. Masami, want to ack it?

-- Steve

> Signed-off-by: Artem Savkov <[email protected]>
> ---
> kernel/trace/trace_kprobe.c | 13 +++++++++++--
> 1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index 21f718472942..fb887ced5056 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -400,11 +400,10 @@ static struct trace_kprobe *find_trace_kprobe(const char *event,
> static int
> enable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file)
> {
> + struct event_file_link *link;
> int ret = 0;
>
> if (file) {
> - struct event_file_link *link;
> -
> link = kmalloc(sizeof(*link), GFP_KERNEL);
> if (!link) {
> ret = -ENOMEM;
> @@ -424,6 +423,16 @@ enable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file)
> else
> ret = enable_kprobe(&tk->rp.kp);
> }
> +
> + if (ret) {
> + if (file) {
> + list_del(&link->list);
> + kfree(link);
> + tk->tp.flags &= ~TP_FLAG_TRACE;
> + } else {
> + tk->tp.flags &= ~TP_FLAG_PROFILE;
> + }
> + }
> out:
> return ret;
> }

2018-07-25 13:57:45

by Josh Poimboeuf

Subject: Re: [PATCH] kprobes: fix trace_probe flags in enable_trace_kprobe

On Wed, Jul 25, 2018 at 12:28:26PM +0200, Artem Savkov wrote:
> If enable_trace_kprobe fails to enable the probe in enable_k(ret)probe
> it returns an error, but does not unset the tp flags it set previosly.

"previously"

> @@ -424,6 +423,16 @@ enable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file)
> else
> ret = enable_kprobe(&tk->rp.kp);
> }
> +
> + if (ret) {
> + if (file) {
> + list_del(&link->list);

Should this be list_del_rcu(), since it was added to the list with
list_add_tail_rcu()?

--
Josh

2018-07-25 14:07:01

by Steven Rostedt

Subject: Re: [PATCH] kprobes: fix trace_probe flags in enable_trace_kprobe

On Wed, 25 Jul 2018 08:56:32 -0500
Josh Poimboeuf <[email protected]> wrote:

> On Wed, Jul 25, 2018 at 12:28:26PM +0200, Artem Savkov wrote:
> > If enable_trace_kprobe fails to enable the probe in enable_k(ret)probe
> > it returns an error, but does not unset the tp flags it set previosly.
>
> "previously"

I tentatively added this to my queue. I updated the subject as:

tracing/kprobes: Fix trace_probe flags on enable_trace_kprobe() failure

But yeah, that needs to be fixed.

>
> > @@ -424,6 +423,16 @@ enable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file)
> > else
> > ret = enable_kprobe(&tk->rp.kp);
> > }
> > +
> > + if (ret) {
> > + if (file) {
> > + list_del(&link->list);
>
> Should this be list_del_rcu(), since it was added to the list with
> list_add_tail_rcu()?
>

Good catch. Yes, that should be list_del_rcu().

Artem,

Can you send a v2 with the changes.

Thanks,

-- Steve

2018-07-25 15:36:52

by Masami Hiramatsu

Subject: Re: [PATCH] kprobes: fix trace_probe flags in enable_trace_kprobe

On Wed, 25 Jul 2018 09:21:51 -0400
Steven Rostedt <[email protected]> wrote:

>
> [ Adding Masami to Cc ]
>
> On Wed, 25 Jul 2018 12:28:26 +0200
> Artem Savkov <[email protected]> wrote:
>
> > If enable_trace_kprobe fails to enable the probe in enable_k(ret)probe
> > it returns an error, but does not unset the tp flags it set previosly.
> > This results in a probe being considered enabled and failures like being
> > unable to remove the probe through kprobe_events file since probes_open()
> > expects every probe to be disabled.
> >
>
> Looks good to me. Masami, want to ack it?

Yes, looks good to me too.

Acked-by: Masami Hiramatsu <[email protected]>

Thanks Artem!

>
> -- Steve
>
> > Signed-off-by: Artem Savkov <[email protected]>
> > ---
> > kernel/trace/trace_kprobe.c | 13 +++++++++++--
> > 1 file changed, 11 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> > index 21f718472942..fb887ced5056 100644
> > --- a/kernel/trace/trace_kprobe.c
> > +++ b/kernel/trace/trace_kprobe.c
> > @@ -400,11 +400,10 @@ static struct trace_kprobe *find_trace_kprobe(const char *event,
> > static int
> > enable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file)
> > {
> > + struct event_file_link *link;
> > int ret = 0;
> >
> > if (file) {
> > - struct event_file_link *link;
> > -
> > link = kmalloc(sizeof(*link), GFP_KERNEL);
> > if (!link) {
> > ret = -ENOMEM;
> > @@ -424,6 +423,16 @@ enable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file)
> > else
> > ret = enable_kprobe(&tk->rp.kp);
> > }
> > +
> > + if (ret) {
> > + if (file) {
> > + list_del(&link->list);
> > + kfree(link);
> > + tk->tp.flags &= ~TP_FLAG_TRACE;
> > + } else {
> > + tk->tp.flags &= ~TP_FLAG_PROFILE;
> > + }
> > + }
> > out:
> > return ret;
> > }
>


--
Masami Hiramatsu <[email protected]>