On Tue, Aug 31, 2021 at 02:54:50PM +0100, Catalin Marinas wrote: > An arm64-specific workaround would be for pagefault_disable() to disable > tag checking. It's a pretty big hammer, weakening the out of bounds > access detection of MTE. My preference would be a fix in the btrfs code. > > A btrfs option would be for copy_to_sk() to return an indication of > where the fault occurred and get fault_in_pages_writeable() to check > that location, even if the copying would restart from an earlier offset > (this requires open-coding copy_to_user_nofault()). An attempt below, > untested and does not cover read_extent_buffer_to_user_nofault(): Umm... There's another copy_to_user_nofault() call in the same function (same story, AFAICS). Can't say I'm fond of their ABI, but then I guess it could've been worse - iterating over btree, running a user-supplied chunk of INTERCAL over it, with all details of internal representation cast in stone by that exposure...
