diff mbox series

[v2] fprobe: add unlock to match a succeeded ftrace_test_recursion_trylock

Message ID 20230703092336.268371-1-zegao@tencent.com
State New
Headers
Series [v2] fprobe: add unlock to match a succeeded ftrace_test_recursion_trylock |

Commit Message

Ze Gao July 3, 2023, 9:23 a.m. UTC 
  Unlock ftrace recursion lock when fprobe_kprobe_handler() is failed
because of some running kprobe.

Fixes: 3cc4e2c5fbae ("fprobe: make fprobe_kprobe_handler recursion free")
Reported-by: Yafang <laoar.shao@gmail.com>
Closes: https://lore.kernel.org/linux-trace-kernel/CALOAHbC6UpfFOOibdDiC7xFc5YFUgZnk3MZ=3Ny6we=AcrNbew@mail.gmail.com/
Signed-off-by: Ze Gao <zegao@tencent.com>
---
 kernel/trace/fprobe.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Comments

Masami Hiramatsu (Google) July 3, 2023, 10:01 a.m. UTC | #1 
On Mon,  3 Jul 2023 17:23:36 +0800
Ze Gao <zegao2021@gmail.com> wrote:

> Unlock ftrace recursion lock when fprobe_kprobe_handler() is failed
> because of some running kprobe.
> 

Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Thanks!

> Fixes: 3cc4e2c5fbae ("fprobe: make fprobe_kprobe_handler recursion free")
> Reported-by: Yafang <laoar.shao@gmail.com>
> Closes: https://lore.kernel.org/linux-trace-kernel/CALOAHbC6UpfFOOibdDiC7xFc5YFUgZnk3MZ=3Ny6we=AcrNbew@mail.gmail.com/
> Signed-off-by: Ze Gao <zegao@tencent.com>
> ---
>  kernel/trace/fprobe.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
> index 18d36842faf5..93b3e361bb97 100644
> --- a/kernel/trace/fprobe.c
> +++ b/kernel/trace/fprobe.c
> @@ -102,12 +102,14 @@ static void fprobe_kprobe_handler(unsigned long ip, unsigned long parent_ip,
>  
>  	if (unlikely(kprobe_running())) {
>  		fp->nmissed++;
> -		return;
> +		goto recursion_unlock;
>  	}
>  
>  	kprobe_busy_begin();
>  	__fprobe_handler(ip, parent_ip, ops, fregs);
>  	kprobe_busy_end();
> +
> +recursion_unlock:
>  	ftrace_test_recursion_unlock(bit);
>  }
>  
> -- 
> 2.40.1
>
Yafang Shao July 3, 2023, 1:44 p.m. UTC | #2 
On Mon, Jul 3, 2023 at 5:23 PM Ze Gao <zegao2021@gmail.com> wrote:
>
> Unlock ftrace recursion lock when fprobe_kprobe_handler() is failed
> because of some running kprobe.
>
> Fixes: 3cc4e2c5fbae ("fprobe: make fprobe_kprobe_handler recursion free")
> Reported-by: Yafang <laoar.shao@gmail.com>
> Closes: https://lore.kernel.org/linux-trace-kernel/CALOAHbC6UpfFOOibdDiC7xFc5YFUgZnk3MZ=3Ny6we=AcrNbew@mail.gmail.com/
> Signed-off-by: Ze Gao <zegao@tencent.com>

Acked-by: Yafang Shao <laoar.shao@gmail.com>

> ---
>  kernel/trace/fprobe.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
> index 18d36842faf5..93b3e361bb97 100644
> --- a/kernel/trace/fprobe.c
> +++ b/kernel/trace/fprobe.c
> @@ -102,12 +102,14 @@ static void fprobe_kprobe_handler(unsigned long ip, unsigned long parent_ip,
>
>         if (unlikely(kprobe_running())) {
>                 fp->nmissed++;
> -               return;
> +               goto recursion_unlock;
>         }
>
>         kprobe_busy_begin();
>         __fprobe_handler(ip, parent_ip, ops, fregs);
>         kprobe_busy_end();
> +
> +recursion_unlock:
>         ftrace_test_recursion_unlock(bit);
>  }
>
> --
> 2.40.1
>
Steven Rostedt July 6, 2023, 4:09 p.m. UTC | #3 
On Mon,  3 Jul 2023 17:23:36 +0800
Ze Gao <zegao2021@gmail.com> wrote:

> Unlock ftrace recursion lock when fprobe_kprobe_handler() is failed
> because of some running kprobe.
> 
> Fixes: 3cc4e2c5fbae ("fprobe: make fprobe_kprobe_handler recursion free")
> Reported-by: Yafang <laoar.shao@gmail.com>
> Closes: https://lore.kernel.org/linux-trace-kernel/CALOAHbC6UpfFOOibdDiC7xFc5YFUgZnk3MZ=3Ny6we=AcrNbew@mail.gmail.com/
> Signed-off-by: Ze Gao <zegao@tencent.com>

Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>

> ---
>  kernel/trace/fprobe.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
> index 18d36842faf5..93b3e361bb97 100644
> --- a/kernel/trace/fprobe.c
> +++ b/kernel/trace/fprobe.c
> @@ -102,12 +102,14 @@ static void fprobe_kprobe_handler(unsigned long ip, unsigned long parent_ip,
>  
>  	if (unlikely(kprobe_running())) {

Off topic for this patch, but Masami, what's the purpose of not calling the
fprobe when a kprobe is running? Does that mean it has probed another kprobe?

Probably could add a comment here to explain the issue.

-- Steve


>  		fp->nmissed++;
> -		return;
> +		goto recursion_unlock;
>  	}
>  
>  	kprobe_busy_begin();
>  	__fprobe_handler(ip, parent_ip, ops, fregs);
>  	kprobe_busy_end();
> +
> +recursion_unlock:
>  	ftrace_test_recursion_unlock(bit);
>  }
>
Masami Hiramatsu (Google) July 7, 2023, 12:15 a.m. UTC | #4 
On Thu, 6 Jul 2023 12:09:16 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Mon,  3 Jul 2023 17:23:36 +0800
> Ze Gao <zegao2021@gmail.com> wrote:
> 
> > Unlock ftrace recursion lock when fprobe_kprobe_handler() is failed
> > because of some running kprobe.
> > 
> > Fixes: 3cc4e2c5fbae ("fprobe: make fprobe_kprobe_handler recursion free")
> > Reported-by: Yafang <laoar.shao@gmail.com>
> > Closes: https://lore.kernel.org/linux-trace-kernel/CALOAHbC6UpfFOOibdDiC7xFc5YFUgZnk3MZ=3Ny6we=AcrNbew@mail.gmail.com/
> > Signed-off-by: Ze Gao <zegao@tencent.com>
> 
> Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> 
> > ---
> >  kernel/trace/fprobe.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
> > index 18d36842faf5..93b3e361bb97 100644
> > --- a/kernel/trace/fprobe.c
> > +++ b/kernel/trace/fprobe.c
> > @@ -102,12 +102,14 @@ static void fprobe_kprobe_handler(unsigned long ip, unsigned long parent_ip,
> >  
> >  	if (unlikely(kprobe_running())) {
> 
> Off topic for this patch, but Masami, what's the purpose of not calling the
> fprobe when a kprobe is running? Does that mean it has probed another kprobe?

This is for the user who is sharing their handler with kprobes (like eBPF),
which may expect that the handler is not called recursively. (e.g. an interrupt
happens while kprobe handler is running and that interrupt calls a function
which is fprobed)

> 
> Probably could add a comment here to explain the issue.

OK, it is also documented in Documentation/trace/fprobe.rst, but it is better
to comment in the code too.

Thanks,

> 
> -- Steve
> 
> 
> >  		fp->nmissed++;
> > -		return;
> > +		goto recursion_unlock;
> >  	}
> >  
> >  	kprobe_busy_begin();
> >  	__fprobe_handler(ip, parent_ip, ops, fregs);
> >  	kprobe_busy_end();
> > +
> > +recursion_unlock:
> >  	ftrace_test_recursion_unlock(bit);
> >  }
> >  
>
diff mbox series

Patch

diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
index 18d36842faf5..93b3e361bb97 100644
--- a/kernel/trace/fprobe.c
+++ b/kernel/trace/fprobe.c
@@ -102,12 +102,14 @@  static void fprobe_kprobe_handler(unsigned long ip, unsigned long parent_ip,
 
 	if (unlikely(kprobe_running())) {
 		fp->nmissed++;
-		return;
+		goto recursion_unlock;
 	}
 
 	kprobe_busy_begin();
 	__fprobe_handler(ip, parent_ip, ops, fregs);
 	kprobe_busy_end();
+
+recursion_unlock:
 	ftrace_test_recursion_unlock(bit);
 }