linux-kernel - Re: [patch] add /proc/pid/stack to dump task's stack trace

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Message-ID: <20081107004824.GA28780@x200.localdomain>
Date:	Fri, 7 Nov 2008 03:48:24 +0300
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Ken Chen <kenchen@...gle.com>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: [patch] add /proc/pid/stack to dump task's stack trace

On Thu, Nov 06, 2008 at 04:30:23PM -0800, Ken Chen wrote:
> On Thu, Nov 6, 2008 at 12:35 PM, Ingo Molnar <mingo@...e.hu> wrote:
> >> +static int proc_pid_stack(struct task_struct *task, char *buffer)
> >> +{
> >> +     for (i = 0; i < trace.nr_entries; i++) {
> >> +             len += sprintf(buffer + len, "[<%p>] %pS\n",
> >> +                             (void *)entries[i], (void
> >> *)entries[i]);
> >
> > hm, this looks like a potential buffer overflow - isnt 'buffer' here
> > only valid up to the next PAGE_SIZE boundary?

So, make trace depth low enough, or even better use seqfiles, if you're
scared by buffer overflows.

> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -130,6 +131,12 @@ struct pid_entry {
>  		{ .proc_show = &proc_##OTYPE } )
>  
>  /*
> + * buffer size used for proc read.  See proc_info_read().
> + * 4K page size but our output routines use some slack for overruns
> + */
> +#define PROC_BLOCK_SIZE	(3*1024)
--
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