Re: linux-next: manual merge of the selinux tree

[Andrew Morton <akpm@linux-foundation.org>]

On Mon, 07 Jul 2008 10:47:34 -0400 Stephen Smalley <sds@tycho.nsa.gov> wrote:

> 
> On Tue, 2008-07-08 at 00:43 +1000, James Morris wrote:
> > On Mon, 7 Jul 2008, Stephen Rothwell wrote:
> > 
> > > Hi all,
> > > 
> > > Today's linux-next merge of the selinux tree got a conflict in
> > > fs/proc/task_mmu.c between commit
> > > 5d7e0d2bd98ef4f5a16ac9da1987ae655368dd6a ("Fix pagemap_read() use of
> > > struct mm_walk") from Linus' tree and commit
> > > ca9b1a1413bac6ea5e5c8cb81044a39bdb3b4bc8 ("Security: split proc ptrace
> > > checking into read vs. attach") from the selinux tree.
> > > 
> > > The former removed some of the code that the latter changed.  It is
> > > probably worth a check on the code in pagemap_read to make sure I got it
> > > right.
> > 
> > I couldn't locate your updated version, but have resolved it in my own 
> > tree (which is being rebased).  
> > 
> > One thing we need to understand is why there were two separate 
> > ptrace_may_attach() calls in the earlier version of pagemap_read().
> 
> It could sleep in between the two calls.
> 

This is basically meaningless?  Other threads could be running, accessing
this mm_struct.  Other processes can be doing stuff.  Preemption can
happen.

Are we missing some locking here?