* Carlos Llamas <cmllamas@xxxxxxxxxx> [220830 15:41]: > On Tue, Aug 30, 2022 at 07:06:37PM +0000, Liam Howlett wrote: > > > diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c > > > index 51f4e1c5cd01..9b1778c00610 100644 > > > --- a/drivers/android/binder_alloc.c > > > +++ b/drivers/android/binder_alloc.c > > > @@ -322,7 +322,6 @@ static inline void binder_alloc_set_vma(struct binder_alloc *alloc, > > > */ > > > if (vma) { > > > vm_start = vma->vm_start; > > > - alloc->vma_vm_mm = vma->vm_mm; > > > > Is this really the null pointer dereference? We check for vma above..? > > > > Not here. The sequence leading to the null-ptr-deref happens when we try > to take alloc->vma_vm_mm->mmap_lock in binder_alloc_new_buf_locked() and > in binder_alloc_print_pages() without initializing alloc->vma_vm_mm > first (e.g. mmap() was never called). These sequences are described in > the commit message but basically they translate to mmap_read_lock(NULL) > calls. Ah, this is unnecessary with the rest of the change. Feel free to add my reviewed-by if you want. Reviewed-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>