linux-kernel - Re: [PATCH v3 18/20] x86/ftrace: Use vmalloc special flag

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Date:   Thu, 21 Feb 2019 19:22:10 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Rick Edgecombe <rick.p.edgecombe@...el.com>
Cc:     Andy Lutomirski <luto@...nel.org>, Ingo Molnar <mingo@...hat.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org, hpa@...or.com,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Nadav Amit <nadav.amit@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>, linux_dti@...oud.com,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, akpm@...ux-foundation.org,
        kernel-hardening@...ts.openwall.com, linux-mm@...ck.org,
        will.deacon@....com, ard.biesheuvel@...aro.org,
        kristen@...ux.intel.com, deneen.t.dock@...el.com
Subject: Re: [PATCH v3 18/20] x86/ftrace: Use vmalloc special flag

On Thu, 21 Feb 2019 15:44:49 -0800
Rick Edgecombe <rick.p.edgecombe@...el.com> wrote:

> Use new flag VM_FLUSH_RESET_PERMS for handling freeing of special
> permissioned memory in vmalloc and remove places where memory was set NX
> and RW before freeing which is no longer needed.
> 
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Acked-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
> ---
>  arch/x86/kernel/ftrace.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
> index 13c8249b197f..93efe3955333 100644
> --- a/arch/x86/kernel/ftrace.c
> +++ b/arch/x86/kernel/ftrace.c
> @@ -692,10 +692,6 @@ static inline void *alloc_tramp(unsigned long size)
>  }
>  static inline void tramp_free(void *tramp, int size)

As size is no longer used within the function, can you remove that too.

Thanks,

-- Steve

>  {
> -	int npages = PAGE_ALIGN(size) >> PAGE_SHIFT;
> -
> -	set_memory_nx((unsigned long)tramp, npages);
> -	set_memory_rw((unsigned long)tramp, npages);
>  	module_memfree(tramp);
>  }
>  #else
> @@ -820,6 +816,8 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
>  	/* ALLOC_TRAMP flags lets us know we created it */
>  	ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP;
>  
> +	set_vm_flush_reset_perms(trampoline);
> +
>  	/*
>  	 * Module allocation needs to be completed by making the page
>  	 * executable. The page is still writable, which is a security hazard,