Re: [PATCH AUTOSEL 4.19 11/29] binder: take read mode of mmap_sem in binder_alloc_free_page()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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@canonical.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