From 88640e1dcd089879530a49a8d212d1814678dfe7 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Tue, 14 May 2019 13:24:39 -0700 Subject: x86/speculation/mds: Revert CPU buffer clear on double fault exit The double fault ESPFIX path doesn't return to user mode at all -- it returns back to the kernel by simulating a #GP fault. prepare_exit_to_usermode() will run on the way out of general_protection before running user code. Signed-off-by: Andy Lutomirski Cc: Borislav Petkov Cc: Frederic Weisbecker Cc: Greg Kroah-Hartman Cc: Jon Masters Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: stable@vger.kernel.org Fixes: 04dcbdb80578 ("x86/speculation/mds: Clear CPU buffers on exit to user") Link: http://lkml.kernel.org/r/ac97612445c0a44ee10374f6ea79c222fe22a5c4.1557865329.git.luto@kernel.org Signed-off-by: Ingo Molnar --- Documentation/x86/mds.rst | 7 ------- 1 file changed, 7 deletions(-) (limited to 'Documentation/x86/mds.rst') diff --git a/Documentation/x86/mds.rst b/Documentation/x86/mds.rst index 534e9baa4e1d..0dc812bb9249 100644 --- a/Documentation/x86/mds.rst +++ b/Documentation/x86/mds.rst @@ -158,13 +158,6 @@ Mitigation points mitigated on the return from do_nmi() to provide almost complete coverage. - - Double fault (#DF): - - A double fault is usually fatal, but the ESPFIX workaround, which can - be triggered from user space through modify_ldt(2) is a recoverable - double fault. #DF uses the paranoid exit path, so explicit mitigation - in the double fault handler is required. - - Machine Check Exception (#MC): Another corner case is a #MC which hits between the CPU buffer clear -- cgit v1.2.3