| Message ID | 20230516023514.2643054-2-pcc@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm: Fix bug affecting swapping in MTE tagged pages | expand |
On 16.05.23 04:35, Peter Collingbourne wrote: > Commit c145e0b47c77 ("mm: streamline COW logic in do_swap_page()") moved > the call to swap_free() before the call to set_pte_at(), which meant that > the MTE tags could end up being freed before set_pte_at() had a chance > to restore them. Fix it by adding a call to the arch_swap_restore() hook > before the call to swap_free(). > > Signed-off-by: Peter Collingbourne <pcc@google.com> > Link: https://linux-review.googlesource.com/id/I6470efa669e8bd2f841049b8c61020c510678965 > Cc: <stable@vger.kernel.org> # 6.1 > Fixes: c145e0b47c77 ("mm: streamline COW logic in do_swap_page()") > Reported-by: Qun-wei Lin (林群崴) <Qun-wei.Lin@mediatek.com> > Link: https://lore.kernel.org/all/5050805753ac469e8d727c797c2218a9d780d434.camel@mediatek.com/ > --- > v2: > - Call arch_swap_restore() directly instead of via arch_do_swap_page() > > mm/memory.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/mm/memory.c b/mm/memory.c > index 01a23ad48a04..a2d9e6952d31 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -3914,6 +3914,13 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) > } > } > > + /* > + * Some architectures may have to restore extra metadata to the page > + * when reading from swap. This metadata may be indexed by swap entry > + * so this must be called before swap_free(). > + */ > + arch_swap_restore(entry, folio); > + > /* > * Remove the swap entry and conditionally try to free up the swapcache. > * We're already holding a reference on the page but haven't mapped it Looks much better to me, thanks :) ... staring at unuse_pte(), I suspect it also doesn't take care of MTE tags and needs fixing?
On Tue, May 16, 2023 at 5:49 AM David Hildenbrand <david@redhat.com> wrote: > > On 16.05.23 04:35, Peter Collingbourne wrote: > > Commit c145e0b47c77 ("mm: streamline COW logic in do_swap_page()") moved > > the call to swap_free() before the call to set_pte_at(), which meant that > > the MTE tags could end up being freed before set_pte_at() had a chance > > to restore them. Fix it by adding a call to the arch_swap_restore() hook > > before the call to swap_free(). > > > > Signed-off-by: Peter Collingbourne <pcc@google.com> > > Link: https://linux-review.googlesource.com/id/I6470efa669e8bd2f841049b8c61020c510678965 > > Cc: <stable@vger.kernel.org> # 6.1 > > Fixes: c145e0b47c77 ("mm: streamline COW logic in do_swap_page()") > > Reported-by: Qun-wei Lin (林群崴) <Qun-wei.Lin@mediatek.com> > > Link: https://lore.kernel.org/all/5050805753ac469e8d727c797c2218a9d780d434.camel@mediatek.com/ > > --- > > v2: > > - Call arch_swap_restore() directly instead of via arch_do_swap_page() > > > > mm/memory.c | 7 +++++++ > > 1 file changed, 7 insertions(+) > > > > diff --git a/mm/memory.c b/mm/memory.c > > index 01a23ad48a04..a2d9e6952d31 100644 > > --- a/mm/memory.c > > +++ b/mm/memory.c > > @@ -3914,6 +3914,13 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) > > } > > } > > > > + /* > > + * Some architectures may have to restore extra metadata to the page > > + * when reading from swap. This metadata may be indexed by swap entry > > + * so this must be called before swap_free(). > > + */ > > + arch_swap_restore(entry, folio); > > + > > /* > > * Remove the swap entry and conditionally try to free up the swapcache. > > * We're already holding a reference on the page but haven't mapped it > > Looks much better to me, thanks :) > > ... staring at unuse_pte(), I suspect it also doesn't take care of MTE > tags and needs fixing? Nice catch, I've fixed it in v3. I don't think there are any other cases like this. I looked for code that decrements the MM_SWAPENTS counter and we're already covering all of them. Peter
diff --git a/mm/memory.c b/mm/memory.c index 01a23ad48a04..a2d9e6952d31 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3914,6 +3914,13 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) } } + /* + * Some architectures may have to restore extra metadata to the page + * when reading from swap. This metadata may be indexed by swap entry + * so this must be called before swap_free(). + */ + arch_swap_restore(entry, folio); + /* * Remove the swap entry and conditionally try to free up the swapcache. * We're already holding a reference on the page but haven't mapped it
Commit c145e0b47c77 ("mm: streamline COW logic in do_swap_page()") moved the call to swap_free() before the call to set_pte_at(), which meant that the MTE tags could end up being freed before set_pte_at() had a chance to restore them. Fix it by adding a call to the arch_swap_restore() hook before the call to swap_free(). Signed-off-by: Peter Collingbourne <pcc@google.com> Link: https://linux-review.googlesource.com/id/I6470efa669e8bd2f841049b8c61020c510678965 Cc: <stable@vger.kernel.org> # 6.1 Fixes: c145e0b47c77 ("mm: streamline COW logic in do_swap_page()") Reported-by: Qun-wei Lin (林群崴) <Qun-wei.Lin@mediatek.com> Link: https://lore.kernel.org/all/5050805753ac469e8d727c797c2218a9d780d434.camel@mediatek.com/ --- v2: - Call arch_swap_restore() directly instead of via arch_do_swap_page() mm/memory.c | 7 +++++++ 1 file changed, 7 insertions(+)