On Wed, 18 Oct 2023 23:15:31 +0800 Baoquan He <bhe@xxxxxxxxxx> wrote: > From: Baoquan He <bhe@xxxxxxxxxx> > Date: Wed, 18 Oct 2023 22:50:14 +0800 > Subject: [PATCH] mm/vmalloc: fix the unchecked dereference warning in vread_iter() > Content-type: text/plain > > LKP reported smatch warning as below: > > =================== > smatch warnings: > mm/vmalloc.c:3689 vread_iter() error: we previously assumed 'vm' could be null (see line 3667) > ...... > 06c8994626d1b7 @3667 size = vm ? get_vm_area_size(vm) : va_size(va); > ...... > 06c8994626d1b7 @3689 else if (!(vm->flags & VM_IOREMAP)) > ^^^^^^^^^ > Unchecked dereference > ===================== > > So add checking on whether 'vm' is not null when dereferencing it in > vread_iter(). This mutes smatch complaint. > > ... > > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -3813,7 +3813,7 @@ long vread_iter(struct iov_iter *iter, const char *addr, size_t count) > > if (flags & VMAP_RAM) > copied = vmap_ram_vread_iter(iter, addr, n, flags); > - else if (!(vm->flags & VM_IOREMAP)) > + else if (!(vm && (vm->flags & VM_IOREMAP))) > copied = aligned_vread_iter(iter, addr, n); > else /* IOREMAP area is treated as memory hole */ > copied = zero_iter(iter, n); So is this not a real runtime bug? We're only doing this to suppress a smatch warning? If so, can we please include a description of *why* this wasn't a bug? What conditions ensure that vm!=NULL at this point?
