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

Greg KH
2023-10-07T11:18:58Z

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@quicinc.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