linux-kernel - Re: [PATCH] binder: add mutex_lock for mmap and NULL when free

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Message-ID: <2023100725-oversized-shore-c873@gregkh>
Date:   Sat, 7 Oct 2023 13:18:52 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Kassey Li <quic_yingangl@...cinc.com>
Cc:     gregkh@...gle.com, cmllamas@...gle.com, surenb@...gle.com,
        arve@...roid.com, joel@...lfernandes.org, brauner@...nel.org,
        tkjos@...roid.com, maco@...roid.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] binder: add mutex_lock for mmap and NULL when free

On Sat, Oct 07, 2023 at 07:07:40PM +0800, Kassey Li wrote:
> 
> 
> On 2023/10/7 14:44, Greg KH wrote:
> > On Sat, Oct 07, 2023 at 11:40:46AM +0800, Kassey Li wrote:
> > > Enforce alloc->mutex in binder_alloc_mmap_handler when add
> > > the entry to list.
> > > 
> > > Assign the freed pages/page_ptr to NULL to catch possible
> > > use after free with NULL pointer access.
> > > 
> > > Signed-off-by: Kassey Li <quic_yingangl@...cinc.com>
> > > ---
> > >   drivers/android/binder_alloc.c | 5 ++++-
> > >   1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> > What commit id does this fix?
> 
>   there is no specific commit id this change going to fix.
> 
>   it is a follow up for commit
> 	19c987241ca1216a51118b2bd0185b8bc5081783  binder: separate out binder_alloc
> functions (mutex lock added for list access in alloc/free)
> 	f2517eb76f1f2f7f89761f9db2b202e89931738c  android: binder: Add global lru
> shrinker to binder (set page->page_ptr = NULL;)
> 
>   the background to raise this change that we are easy hit below crash in
> monkey test:
> 
> where a wrong end is passing to
> binder_update_page_range, thus calculate a weird index
> for
>   page = &alloc->pages[index]

Obviously it is a fix for some commit, please list that here.

thanks,

greg k-h