linux-kernel - Re: [PATCH AUTOSEL 4.19 11/29] binder: take read mode of mmap_sem in binder_alloc_free

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Date:   Fri, 30 Aug 2019 08:29:10 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Tyler Hicks <tyhicks@...onical.com>
Cc:     Sasha Levin <sashal@...nel.org>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, Todd Kjos <tkjos@...roid.com>,
        devel@...verdev.osuosl.org
Subject: Re: [PATCH AUTOSEL 4.19 11/29] binder: take read mode of mmap_sem in
 binder_alloc_free_page()

On Thu, Aug 29, 2019 at 10:13:20AM -0500, Tyler Hicks wrote:
> Hello, Sasha!
> 
> On 2019-08-29 06:49:51, Sasha Levin wrote:
> > From: Tyler Hicks <tyhicks@...onical.com>
> > 
> > [ Upstream commit 60d4885710836595192c42d3e04b27551d30ec91 ]
> > 
> > Restore the behavior of locking mmap_sem for reading in
> > binder_alloc_free_page(), as was first done in commit 3013bf62b67a
> > ("binder: reduce mmap_sem write-side lock"). That change was
> > inadvertently reverted by commit 5cec2d2e5839 ("binder: fix race between
> > munmap() and direct reclaim").
> > 
> > In addition, change the name of the label for the error path to
> > accurately reflect that we're taking the lock for reading.
> > 
> > Backporting note: This fix is only needed when *both* of the commits
> > mentioned above are applied. That's an unlikely situation since they
> > both landed during the development of v5.1 but only one of them is
> > targeted for stable.
> 
> This patch isn't meant to be applied to 4.19 since commit 3013bf62b67a
> ("binder: reduce mmap_sem write-side lock") was never brought back to
> 4.19.
> 
> Tyler
> 
> > 
> > Fixes: 5cec2d2e5839 ("binder: fix race between munmap() and direct reclaim")

But this commit is in 4.19.49

thanks,

greg k-h