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/I6470efa669e8bd2f841049b8c61020c510... 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@m...
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 itLooks 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