Re: [PATCH][RFC] 2.5.42: remove capable(CAP_SYS_RAWIO) check from open_kmem

[Chris Wright <chris@wirex.com>]

* Olaf Dietsche (olaf.dietsche#list.linux-kernel@t-online.de) wrote:
> Olaf Dietsche <olaf.dietsche#list.linux-kernel@t-online.de> writes:
> 
> > In drivers/char/mem.c there's open_port(), which is used as open_mem()
> > and open_kmem() as well. I don't see the benefit of this, since
> > /dev/mem and /dev/kmem are already protected by filesystem
> > permissions.
> >
> > mem.c, line 526:
> > static int open_port(struct inode * inode, struct file * filp)
> > {
> > 	return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
> > }
> >
> > If anyone knows, why this is done this way, please let me
> > know. Otherwise, I suggest the patch below.
> 
> I haven't got a convincing answer against this patch, so far. The
> patch applies to 2.5.43 as well.
> Linus, please apply.

No way.  This is clearly a bad idea.  CAP_SYS_RAWIO should be treated very
seriously, look at what it enables.  CAP_DAC_OVERRIDE is substantially
less powerful, and if you remove this check, it would be the only
capability protecting this.

-chris
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