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

[Kassey Li]

On 2023/10/7 19:37, Greg KH wrote:
> On Sat, Oct 07, 2023 at 07:34:05PM +0800, Kassey Li wrote:
> > 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.
>
> Odd indentation :(

thanks for the quick suggest and review, based on this version, will do 
below and send patch v2.

./scripts/checkpatch.pl 
0001-binder-add-mutex_lock-for-mmap-and-NULL-when-free.patch
total: 0 errors, 0 warnings, 26 lines checked

0001-binder-add-mutex_lock-for-mmap-and-NULL-when-free.patch has no 
obvious style problems and is ready for submission.

> >      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>
>
> Looks better than before, thanks.
>
> greg k-h