linux-kernel - Re: [PATCH v2] x86: ptrace.h: Make regs_get_kernel_stack

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Date:   Thu, 18 Oct 2018 09:21:06 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Andy Lutomirski <luto@...capital.net>,
        LKML <linux-kernel@...r.kernel.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH v2] x86: ptrace.h: Make regs_get_kernel_stack_nth() not
 fault on bad stack

On Thu, 18 Oct 2018 15:48:46 +0900
Masami Hiramatsu <mhiramat@...nel.org> wrote:

> On Wed, 17 Oct 2018 16:59:51 -0400
> Steven Rostedt <rostedt@...dmis.org> wrote:
> 
> > From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
> > 
> > Andy had some concerns about using regs_get_kernel_stack_nth() in a new
> > function regs_get_kernel_argument() as if there's any error in the stack
> > code, it could cause a bad memory access. To be on the safe side, call
> > probe_kernel_read() on the stack address to be extra careful in accessing
> > the memory. A helper function, regs_get_kernel_stack_nth_addr(), was added
> > to just return the stack address (or NULL if not on the stack), that will be
> > used to find the address (and could be used by other functions) and read the
> > address with kernel_probe_read().
> > 
> > Link: http://lkml.kernel.org/r/CALCETrXn9zKTb9i1LP3qoFcpqZHF34BdkuZ5D3N0uCmRr+VnbA@mail.gmail.com
> > Requested-by: Andy Lutomirski <luto@...capital.net>
> > Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>  
> 
> Looks good to me.
> 
> Reviewed-by: Masami Hiramatsu <mhiramat@...nel.org>
> 
> Thank you,
> 

Thanks Masami,

I plan on posting all the patches later today. They already passed all
my tests :-) Well, it hasn't broken anything, as I haven't added tests
to test your code yet.

-- Steve