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

[Kassey Li]

On 2023/10/7 19:18, Greg KH wrote:
> 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@xxxxxxxxxxx>
> > > > ---
> > > >    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.

 ok, please kindly review this patch description according your 
suggest, i can re-send v2 patch again.

commit 16aaeb8556ff4eb75823c56773ee82b06bac44a0 (HEAD -> master)
Author: Kassey Li <quic_yingangl@xxxxxxxxxxx>
Date:   Thu Sep 28 10:42:52 2023 +0800

    binder: add mutex_lock for mmap and NULL when free

    -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.

    Fixes: 19c987241ca1 ("binder: separate out binder_alloc functions")
    Fixes: f2517eb76f1f ("android: binder: Add global lru shrinker to 
binder")
    Signed-off-by: Kassey Li <quic_yingangl@xxxxxxxxxxx>

> thanks,
>
> greg k-h