On 1/13/25 20:11, Suren Baghdasaryan wrote: > On Mon, Jan 13, 2025 at 9:13 AM Lorenzo Stoakes > <lorenzo.stoakes@xxxxxxxxxx> wrote: >> >> On Mon, Jan 13, 2025 at 09:02:50AM -0800, Suren Baghdasaryan wrote: >> > On Mon, Jan 13, 2025 at 4:05 AM Lorenzo Stoakes >> > <lorenzo.stoakes@xxxxxxxxxx> wrote: >> > > >> > > On Fri, Jan 10, 2025 at 08:25:52PM -0800, Suren Baghdasaryan wrote: >> > > > When exit_mmap() removes vmas belonging to an exiting task, it does not >> > > > mark them as detached since they can't be reached by other tasks and they >> > > > will be freed shortly. Once we introduce vma reuse, all vmas will have to >> > > > be in detached state before they are freed to ensure vma when reused is >> > > > in a consistent state. Add missing vma_mark_detached() before freeing the >> > > > vma. >> > > >> > > Hmm this really makes me worry that we'll see bugs from this detached >> > > stuff, do we make this assumption anywhere else I wonder? >> > >> > This is the only place which does not currently detach the vma before >> > freeing it. If someone tries adding a case like that in the future, >> > they will be met with vma_assert_detached() inside vm_area_free(). >> >> OK good to know! >> >> Again, I wonder if we should make these assertions stronger as commented >> elsewhere, because if we see them in production isn't that worth an actual >> non-debug WARN_ON_ONCE()? > > Sure. I'll change vma_assert_attached()/vma_assert_detached() to use > WARN_ON_ONCE() and to return a bool (see also my reply in the patch > [0/17]). So is this a case of "someone might introduce code later that will violate them" as alluded to above? Unconditional WARN_ON_ONCE seems too much then. In general it's not easy to determine how paranoid we should be in non-debug code, but I'm not sure what's the need here specifically.
