Re: [PATCH V3 03/11] x86: Lock down IO port access when module security is enabled

[James Morris <jmorris@namei.org>]

On Tue, 3 Sep 2013, Matthew Garrett wrote:

> IO port access would permit users to gain access to PCI configuration
> registers, which in turn (on a lot of hardware) give access to MMIO register
> space. This would potentially permit root to trigger arbitrary DMA, so lock
> it down by default.
> 
> Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>


Reviewed-by: James Morris <jmorris@namei.org>




> ---
>  arch/x86/kernel/ioport.c | 5 +++--
>  drivers/char/mem.c       | 4 ++++
>  2 files changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
> index 4ddaf66..00b4403 100644
> --- a/arch/x86/kernel/ioport.c
> +++ b/arch/x86/kernel/ioport.c
> @@ -15,6 +15,7 @@
>  #include <linux/thread_info.h>
>  #include <linux/syscalls.h>
>  #include <linux/bitmap.h>
> +#include <linux/module.h>
>  #include <asm/syscalls.h>
>  
>  /*
> @@ -28,7 +29,7 @@ asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on)
>  
>  	if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
>  		return -EINVAL;
> -	if (turn_on && !capable(CAP_SYS_RAWIO))
> +	if (turn_on && (!capable(CAP_SYS_RAWIO) || secure_modules()))
>  		return -EPERM;
>  
>  	/*
> @@ -103,7 +104,7 @@ SYSCALL_DEFINE1(iopl, unsigned int, level)
>  		return -EINVAL;
>  	/* Trying to gain more privileges? */
>  	if (level > old) {
> -		if (!capable(CAP_SYS_RAWIO))
> +		if (!capable(CAP_SYS_RAWIO) || secure_modules())
>  			return -EPERM;
>  	}
>  	regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | (level << 12);
> diff --git a/drivers/char/mem.c b/drivers/char/mem.c
> index f895a8c..1af8664 100644
> --- a/drivers/char/mem.c
> +++ b/drivers/char/mem.c
> @@ -28,6 +28,7 @@
>  #include <linux/export.h>
>  #include <linux/io.h>
>  #include <linux/aio.h>
> +#include <linux/module.h>
>  
>  #include <asm/uaccess.h>
>  
> @@ -563,6 +564,9 @@ static ssize_t write_port(struct file *file, const char __user *buf,
>  	unsigned long i = *ppos;
>  	const char __user *tmp = buf;
>  
> +	if (secure_modules())
> +		return -EPERM;
> +
>  	if (!access_ok(VERIFY_READ, buf, count))
>  		return -EFAULT;
>  	while (count-- > 0 && i < 65536) {
> -- 
> 1.8.3.1
> 
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-- 
James Morris
<jmorris@namei.org>