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

[Greg Kroah-Hartman]

On Fri, Aug 30, 2019 at 02:30:19AM -0500, Tyler Hicks wrote:
> On 2019-08-30 08:29:10, Greg Kroah-Hartman wrote:
> > 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 at 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
> 
> That's correct but commit 3013bf62b67a isn't present in 4.19.y. See the
> "Backporting note" above.

Heh, I never read that part of the text, nevermind :)

greg k-h