linux-kernel - Re: [PATCH] fprobe: Fix to allocate entry_data

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Message-Id: <20240301075010.6125d953f6e109fe71cf9ffe@kernel.org>
Date: Fri, 1 Mar 2024 07:50:10 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Jiri Olsa <olsajiri@...il.com>
Cc: Steven Rostedt <rostedt@...dmis.org>,
 linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fprobe: Fix to allocate entry_data_size buffer with
 rethook instances

On Thu, 29 Feb 2024 22:58:54 +0100
Jiri Olsa <olsajiri@...il.com> wrote:

> On Thu, Feb 29, 2024 at 08:22:47PM +0900, Masami Hiramatsu (Google) wrote:
> > From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> > 
> > Fix to allocate fprobe::entry_data_size buffer with rethook instances.
> > If fprobe doesn't allocate entry_data_size buffer for each rethook instance,
> > fprobe entry handler can cause a buffer overrun when storing entry data in
> > entry handler.
> > 
> > Reported-by: Jiri Olsa <olsajiri@...il.com>
> 
> Tested-by: Jiri Olsa <olsajiri@...il.com>

Thanks for testing!
Let me pick this to probe/fixes.

Thank you,

> 
> thanks,
> jirka
> 
> > Fixes: 4bbd93455659 ("kprobes: kretprobe scalability improvement")
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> > ---
> >  kernel/trace/fprobe.c |   14 ++++++--------
> >  1 file changed, 6 insertions(+), 8 deletions(-)
> > 
> > diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
> > index 6cd2a4e3afb8..9ff018245840 100644
> > --- a/kernel/trace/fprobe.c
> > +++ b/kernel/trace/fprobe.c
> > @@ -189,9 +189,6 @@ static int fprobe_init_rethook(struct fprobe *fp, int num)
> >  {
> >  	int size;
> >  
> > -	if (num <= 0)
> > -		return -EINVAL;
> > -
> >  	if (!fp->exit_handler) {
> >  		fp->rethook = NULL;
> >  		return 0;
> > @@ -199,15 +196,16 @@ static int fprobe_init_rethook(struct fprobe *fp, int num)
> >  
> >  	/* Initialize rethook if needed */
> >  	if (fp->nr_maxactive)
> > -		size = fp->nr_maxactive;
> > +		num = fp->nr_maxactive;
> >  	else
> > -		size = num * num_possible_cpus() * 2;
> > -	if (size <= 0)
> > +		num *= num_possible_cpus() * 2;
> > +	if (num <= 0)
> >  		return -EINVAL;
> >  
> > +	size = sizeof(struct fprobe_rethook_node) + fp->entry_data_size;
> > +
> >  	/* Initialize rethook */
> > -	fp->rethook = rethook_alloc((void *)fp, fprobe_exit_handler,
> > -				sizeof(struct fprobe_rethook_node), size);
> > +	fp->rethook = rethook_alloc((void *)fp, fprobe_exit_handler, size, num);
> >  	if (IS_ERR(fp->rethook))
> >  		return PTR_ERR(fp->rethook);
> >  
> > 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>