From: Tony Luck <tony.luck@intel.com>
Date: Tue, 17 Aug 2021 17:29:42 -0700
Subject: x86/mce: Drop copyin special case for #MC
Git-commit: 690658471b5f28d306e6492c4585d748cb5304e8
Patch-mainline: v5.16-rc1
References: bsc#1201050 CVE-2021-26341

Fixes to the iterator code to handle faults that are not on page
boundaries mean that the special case for machine check during copy from
user is no longer needed.

For a full list of those fixes, see the output of:

  git log --oneline v5.14 ^v5.13 -- lib/iov_iter.c

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210818002942.1607544-4-tony.luck@intel.com
---
 arch/x86/lib/copy_user_64.S | 13 -------------
 1 file changed, 13 deletions(-)

diff --git a/arch/x86/lib/copy_user_64.S b/arch/x86/lib/copy_user_64.S
index 57b79c577496..2797e630b9b1 100644
--- a/arch/x86/lib/copy_user_64.S
+++ b/arch/x86/lib/copy_user_64.S
@@ -234,24 +234,11 @@ EXPORT_SYMBOL(copy_user_enhanced_fast_string)
  */
 SYM_CODE_START_LOCAL(.Lcopy_user_handle_tail)
 	movl %edx,%ecx
-	cmp $X86_TRAP_MC,%eax		/* check if X86_TRAP_MC */
-	je 3f
 1:	rep movsb
 2:	mov %ecx,%eax
 	ASM_CLAC
 	ret
 
-	/*
-	 * Return zero to pretend that this copy succeeded. This
-	 * is counter-intuitive, but needed to prevent the code
-	 * in lib/iov_iter.c from retrying and running back into
-	 * the poison cache line again. The machine check handler
-	 * will ensure that a SIGBUS is sent to the task.
-	 */
-3:	xorl %eax,%eax
-	ASM_CLAC
-	ret
-
 	_ASM_EXTABLE_CPY(1b, 2b)
 SYM_CODE_END(.Lcopy_user_handle_tail)