Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1651270

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

Show all headers | View raw

On Thu, 25 May 2017 12:51:21 -0700
Kees Cook <keescook@chromium.org> wrote:

> On Thu, May 25, 2017 at 10:46 AM, Luis R. Rodriguez <mcgrof@kernel.org> wrote:
> > 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.
> 
> It seems like it really should. That would put it in a single place
> and avoid this mistake again in the future. Does module_memfree() have
> access to the allocation size, or does that need to get plumbed?

module_memfree() is just a wrapper of vfree, so find_vm_area()
will help us to get the size.

Thank you,


> 
> -Kees
> 
> -- 
> Kees Cook
> Pixel Security


-- 
Masami Hiramatsu <mhiramat@kernel.org>

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

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

csiph-web