On Thu, 26 Feb 2015, Arve Hjønnevåg wrote: > > ----------8<---------- > > --- a/drivers/android/binder.c > > +++ b/drivers/android/binder.c > > @@ -601,6 +601,7 @@ static int binder_update_page_range(struct > > binder_proc *proc, int allocate, > > goto err_alloc_page_failed; > > } > > tmp_area.addr = page_addr; > > + tmp_area.flags &= ~VM_NO_GUARD; > > This variable is not initialized, so I would expect this to add a > warning. Setting it to VM_NO_GUARD and removing, " + PAGE_SIZE /* > guard page? */" fromt he next line would be better. However, the "new" > map_kernel_range_noflush api seems like a better api to use for this, > since it removes the need to create a dummy vm_struct at all. >
Yeah, this is what you want to do and it's a bug in commit 71394fe50146 ("mm: vmalloc: add flag preventing guard hole allocation") that started to look at tmp_area.size without fixing up any of the callers when tmp_area.addr and tmp_area.size were only important in the past. It shouldn't take much work to make this use map_kernel_range_noflush(). > > tmp_area.size = PAGE_SIZE + PAGE_SIZE /* guard page? */; > > ret = map_vm_area(&tmp_area, PAGE_KERNEL, page); > > if (ret) { > > ---------->8----------