On Sat, 29 Jun 2019 22:56:47 +0200 (CEST)
Jiri Kosina wrote:
> > Care to send a patch? :-)
>
> From: Jiri Kosina
> Subject: [PATCH] ftrace/x86: anotate text_mutex split between
> ftrace_arch_code_modify_post_process() and ftrace_arch_code_modify_prepare()
Care to send a proper patch ;-)
As
On Fri, 28 Jun 2019, Steven Rostedt wrote:
> > > > How is that supposed to work?
> > > >
> > > > ftrace
> > > > prepare()
> > > > setrw()
> > > > setro()
> > > > patch <- FAIL
> > >
> > > /me dodges frozen shark
> > >
> > > Yo
On Fri, 28 Jun 2019 19:33:30 +0200 (CEST)
Jiri Kosina wrote:
> On Thu, 27 Jun 2019, Josh Poimboeuf wrote:
>
> > > How is that supposed to work?
> > >
> > > ftrace
> > > prepare()
> > >setrw()
> > > setro()
> > > patch <- FAIL
> >
> > /me dodges f
On Thu, 27 Jun 2019, Josh Poimboeuf wrote:
> > How is that supposed to work?
> >
> > ftrace
> > prepare()
> > setrw()
> > setro()
> > patch <- FAIL
>
> /me dodges frozen shark
>
> You are right of course. My brain has apparently already sh
On Fri, Jun 28, 2019 at 11:46:27AM -0400, Steven Rostedt wrote:
> On Fri, 28 Jun 2019 09:54:24 -0400
> Steven Rostedt wrote:
>
> > On Fri, 28 Jun 2019 12:52:32 +0200
> > Petr Mladek wrote:
> >
> > > On Fri 2019-06-28 09:32:03, Miroslav Benes wrote:
> > > > On Thu, 27 Jun 2019, Petr Mladek wro
On Fri, 28 Jun 2019 09:54:24 -0400
Steven Rostedt wrote:
> On Fri, 28 Jun 2019 12:52:32 +0200
> Petr Mladek wrote:
>
> > On Fri 2019-06-28 09:32:03, Miroslav Benes wrote:
> > > On Thu, 27 Jun 2019, Petr Mladek wrote:
> > > > @@ -2611,12 +2610,10 @@ static void ftrace_run_update_code(int c
On Fri, 28 Jun 2019 12:52:32 +0200
Petr Mladek wrote:
> On Fri 2019-06-28 09:32:03, Miroslav Benes wrote:
> > On Thu, 27 Jun 2019, Petr Mladek wrote:
> > > @@ -2611,12 +2610,10 @@ static void ftrace_run_update_code(int command)
> > > {
> > > int ret;
> > >
> > > - mutex_lock(&text_mutex);
On Fri 2019-06-28 09:32:03, Miroslav Benes wrote:
> On Thu, 27 Jun 2019, Petr Mladek wrote:
> > @@ -2611,12 +2610,10 @@ static void ftrace_run_update_code(int command)
> > {
> > int ret;
> >
> > - mutex_lock(&text_mutex);
> > -
> > ret = ftrace_arch_code_modify_prepare();
> > FTRAC
On Thu, 27 Jun 2019, Petr Mladek wrote:
> The commit 9f255b632bf12c4dd7 ("module: Fix livepatch/ftrace module text
> permissions race") causes a possible deadlock between register_kprobe()
> and ftrace_run_update_code() when ftrace is using stop_machine().
>
> The existing dependency chain (in re
On Thu, Jun 27, 2019 at 09:13:04PM -0400, Steven Rostedt wrote:
> On Thu, 27 Jun 2019 18:19:52 -0500
> Josh Poimboeuf wrote:
>
>
> > Maybe a comment or two would help though.
> >
>
> I'm adding the following change. Care to add a "reviewed-by" for this
> one?
>
> -- Steve
>
> diff --git a/a
On Thu, 27 Jun 2019 18:19:52 -0500
Josh Poimboeuf wrote:
> Maybe a comment or two would help though.
>
I'm adding the following change. Care to add a "reviewed-by" for this
one?
-- Steve
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 33786044d5ac..d7e93b2783fd 100644
On Thu, 27 Jun 2019, Josh Poimboeuf wrote:
> On Fri, Jun 28, 2019 at 01:09:08AM +0200, Thomas Gleixner wrote:
> > On Thu, 27 Jun 2019, Steven Rostedt wrote:
> > > I agree with Josh on this. As the original bug was the race between
> > > ftrace and live patching / modules changing the text from ro t
On Thu, 27 Jun 2019 18:19:52 -0500
Josh Poimboeuf wrote:
> /me dodges frozen shark
>
> You are right of course. My brain has apparently already shut off for
> the day.
And I agreed with your miscalculation. I guess I should have looked
deeper into it. Or have less faith in you ;-)
>
> Maybe
On Fri, Jun 28, 2019 at 01:09:08AM +0200, Thomas Gleixner wrote:
> On Thu, 27 Jun 2019, Steven Rostedt wrote:
> > On Thu, 27 Jun 2019 17:47:29 -0500
> > > Releasing the lock in a separate function seems a bit surprising and
> > > fragile, would it be possible to do something like this instead?
> >
On Fri, 28 Jun 2019 01:09:08 +0200 (CEST)
Thomas Gleixner wrote:
> On Thu, 27 Jun 2019, Steven Rostedt wrote:
> > On Thu, 27 Jun 2019 17:47:29 -0500
> > > Releasing the lock in a separate function seems a bit surprising and
> > > fragile, would it be possible to do something like this instead?
On Thu, 27 Jun 2019, Steven Rostedt wrote:
> On Thu, 27 Jun 2019 17:47:29 -0500
> > Releasing the lock in a separate function seems a bit surprising and
> > fragile, would it be possible to do something like this instead?
> >
> > diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
> >
On Thu, 27 Jun 2019 17:47:29 -0500
Josh Poimboeuf wrote:
> Thanks a lot for fixing this Petr.
>
> On Thu, Jun 27, 2019 at 10:13:34AM +0200, Petr Mladek wrote:
> > @@ -35,6 +36,7 @@
> >
> > int ftrace_arch_code_modify_prepare(void)
> > {
> > + mutex_lock(&text_mutex);
> > set_kernel_tex
Thanks a lot for fixing this Petr.
On Thu, Jun 27, 2019 at 10:13:34AM +0200, Petr Mladek wrote:
> @@ -35,6 +36,7 @@
>
> int ftrace_arch_code_modify_prepare(void)
> {
> + mutex_lock(&text_mutex);
> set_kernel_text_rw();
> set_all_modules_text_rw();
> return 0;
> @@ -44,6 +
On Thu, 27 Jun 2019, Petr Mladek wrote:
> Fortunately, the problematic fix is needed only on x86_64. It is
> the only architecture that calls set_all_modules_text_rw()
> in ftrace path and supports livepatching at the same time.
>
> Therefore it is enough to move text_mutex handling from the gener
The commit 9f255b632bf12c4dd7 ("module: Fix livepatch/ftrace module text
permissions race") causes a possible deadlock between register_kprobe()
and ftrace_run_update_code() when ftrace is using stop_machine().
The existing dependency chain (in reverse order) is:
-> #1 (text_mutex){+.+.}:
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