Re: [PATCH V2] x86/ftrace: Make sure that ftrace trampolines are not RWX

From	"Luis R. Rodriguez" <mcgrof@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH V2] x86/ftrace: Make sure that ftrace trampolines are not RWX
Date	2017-05-25 19:50 +0200
Message-ID	<tL53z-2KJ-7@gated-at.bofh.it> (permalink)
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On Thu, May 25, 2017 at 10:57:51AM +0200, Thomas Gleixner wrote:
> ftrace use module_alloc() to allocate trampoline pages. The mapping of
> module_alloc() is RWX, which makes sense as the memory is written to right
> after allocation. But nothing makes these pages RO after writing to them.
> 
> Add proper set_memory_rw/ro() calls to protect the trampolines after
> modification.
> 
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
>  arch/x86/kernel/ftrace.c |   20 ++++++++++++++------
>  1 file changed, 14 insertions(+), 6 deletions(-)
> 
> --- a/arch/x86/kernel/ftrace.c
> +++ b/arch/x86/kernel/ftrace.c
> @@ -689,8 +689,12 @@ static inline void *alloc_tramp(unsigned
>  {
>  	return module_alloc(size);
>  }
> -static inline void tramp_free(void *tramp)
> +static inline void tramp_free(void *tramp, int size)
>  {
> +	int npages = PAGE_ALIGN(size) >> PAGE_SHIFT;
> +
> +	set_memory_nx((unsigned long)tramp, npages);
> +	set_memory_rw((unsigned long)tramp, npages);
>  	module_memfree(tramp);
>  }

Can/should module_memfree() just do this for users? With Masami's fix that'd
be 2 users already.

   Luis

Thread

Re: [PATCH] x86/ftrace: Make sure that ftrace trampolines are not  RWX Thomas Gleixner <tglx@linutronix.de> - 2017-05-25 08:30 +0200
  [PATCH V2] x86/ftrace: Make sure that ftrace trampolines are not  RWX Thomas Gleixner <tglx@linutronix.de> - 2017-05-25 11:00 +0200
    Re: [PATCH V2] x86/ftrace: Make sure that ftrace trampolines are  not RWX Steven Rostedt <rostedt@goodmis.org> - 2017-05-25 17:20 +0200
    Re: [PATCH V2] x86/ftrace: Make sure that ftrace trampolines are not  RWX "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-05-25 19:50 +0200
      Re: [PATCH V2] x86/ftrace: Make sure that ftrace trampolines are not RWX Kees Cook <keescook@chromium.org> - 2017-05-25 22:00 +0200
        Re: [PATCH V2] x86/ftrace: Make sure that ftrace trampolines are  not RWX Thomas Gleixner <tglx@linutronix.de> - 2017-05-26 09:10 +0200
          Re: [PATCH V2] x86/ftrace: Make sure that ftrace trampolines are not  RWX Heiko Carstens <heiko.carstens@de.ibm.com> - 2017-05-26 11:40 +0200
            Re: [PATCH V2] x86/ftrace: Make sure that ftrace trampolines are  not RWX Thomas Gleixner <tglx@linutronix.de> - 2017-05-26 12:00 +0200
            Re: [PATCH V2] x86/ftrace: Make sure that ftrace trampolines are not RWX Michael Ellerman <mpe@ellerman.id.au> - 2017-05-26 13:50 +0200
        Re: [PATCH V2] x86/ftrace: Make sure that ftrace trampolines are  not RWX Masami Hiramatsu <mhiramat@kernel.org> - 2017-05-26 11:50 +0200
    Re: [PATCH V2] x86/ftrace: Make sure that ftrace trampolines are  not RWX Steven Rostedt <rostedt@goodmis.org> - 2017-05-26 15:40 +0200
      Re: [PATCH V2] x86/ftrace: Make sure that ftrace trampolines are  not RWX Steven Rostedt <rostedt@goodmis.org> - 2017-05-26 16:00 +0200
      Re: [PATCH V2] x86/ftrace: Make sure that ftrace trampolines are  not RWX Thomas Gleixner <tglx@linutronix.de> - 2017-05-26 16:00 +0200

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