linux-kernel - Re: [PATCH 1/2] Staging: android: binder: Add some error checks

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Date:	Wed, 1 Feb 2012 14:47:08 -0800
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Arve Hjønnevåg <arve@...roid.com>
Cc:	Dan Carpenter <dan.carpenter@...cle.com>,
	devel@...verdev.osuosl.org,
	Christopher Lais <chris+android@...thought.org>,
	linux-kernel@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH 1/2] Staging: android: binder: Add some error checks

On Wed, Feb 01, 2012 at 02:29:36PM -0800, Arve Hjønnevåg wrote:
> 2012/1/31 Dan Carpenter <dan.carpenter@...cle.com>:
> > On Tue, Jan 31, 2012 at 03:20:30PM -0800, Arve Hjønnevåg wrote:
> >> 2012/1/31 Greg KH <greg@...ah.com>:
> >> > On Sat, Jan 21, 2012 at 11:22:08AM +0300, Dan Carpenter wrote:
> >> >> On Fri, Jan 20, 2012 at 07:56:20PM -0800, Arve Hjønnevåg wrote:
> >> >> > - Add a mutex to protect against two processes mmapping the
> >> >> >   same binder_proc.
> >> >> > - After locking mmap_sem, check that the vma we want to access
> >> >> >   (still) points to the same mm_struct.
> >> >> > - Use proc->tsk instead of current to get the files struct since
> >> >> >   this is where we get the rlimit from.
> >> >>
> >> >> This doesn't seem related to the locking change at all.  Probably
> >> >> this patch should be split into three patches, one bugfix per
> >> >> patch, unless they are very closely related.
> >> >
> >> > I agree.  Arve, is this all fixing one problem, or multiple ones?  If
> >> > multiple ones, we need this split up into multiple patches.
> >> >
> >>
> >> That depend on your point of view. It fixes crashes if you use the
> >> same binder file pointer from multiple processes. It seemed excessive
> >> to have three patches for this.
> >
> > It would have helped you to write a better changelog.  The subject
> > says "[patch] android: grab bag of random fixes" and the the
> > description matches that.  You have no idea how annoyed I get at
> > grab bag patches.
> >
> 
> Would the following be a better change description (or do you still
> want three patches):
> 
> Staging: android: binder: Fix crashes when sharing a binder file
> between processes
> 
> Opening the binder driver and sharing the file returned with
> other processes (e.g. by calling fork) can crash the kernel.
> Prevent these crashes with the following changes:
> - Add a mutex to protect against two processes mmapping the
>   same binder_proc.
> - After locking mmap_sem, check that the vma we want to access
>   (still) points to the same mm_struct.
> - Use proc->tsk instead of current to get the files struct since
>   this is where we get the rlimit from.

That looks good to me, as one patch, Dan?

greg k-h
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