kaiser: fix regs to do_nmi() ifndef CONFIG_KAISER

pjt has observed that nmi's second (nmi_from_kernel) call to do_nmi()
adjusted the %rdi regs arg, rightly when CONFIG_KAISER, but wrongly
when not CONFIG_KAISER.

Although the minimal change is to add an #ifdef CONFIG_KAISER around
the addq line, that looks cluttered, and I prefer how the first call
to do_nmi() handled it: prepare args in %rdi and %rsi before getting
into the CONFIG_KAISER block, since it does not touch them at all.

And while we're here, place the "#ifdef CONFIG_KAISER" that follows
each, to enclose the "Unconditionally restore CR3" comment: matching
how the "Unconditionally use kernel CR3" comment above is enclosed.

Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 487f0b73d82611a2dc48d7d78409e2e9d994006a)
Orabug: 27333760
CVE: CVE-2017-5754
Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Conflicts:
	arch/x86/entry/entry_64.S (not in this tree)
	arch/x86/kernel/entry_64.S (patched instead of that)

Signed-off-by: Kirtikar Kashyap <kirtikar.kashyap@oracle.com>

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 1b41d6b51b87b131733bd284b088aceb08b50842..070a609dec77488fca71aea455b5e93cb007dbb1 100644 (file)
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1730,12 +1730,12 @@ ENTRY(nmi)
        movq    %rax, %cr3
 #endif
        call    do_nmi
+#ifdef CONFIG_KAISER
        /*
         * Unconditionally restore CR3.  I know we return to
         * kernel code that needs user CR3, but do we ever return
         * to "user mode" where we need the kernel CR3?
         */
-#ifdef CONFIG_KAISER
        popq    %rax
        mov     %rax, %cr3
 #endif
@@ -1955,6 +1955,8 @@ end_repeat_nmi:
        SWAPGS
        xorl    %ebx, %ebx
 1:
+       movq    %rsp, %rdi
+       movq    $-1, %rsi
 #ifdef CONFIG_KAISER
        /* Unconditionally use kernel CR3 for do_nmi() */
        /* %rax is saved above, so OK to clobber here */
@@ -1968,16 +1970,13 @@ end_repeat_nmi:
        DEFAULT_FRAME 0                         /* XXX: Do we need this? */
 
        /* paranoidentry do_nmi, 0; without TRACE_IRQS_OFF */
-       movq %rsp,%rdi
-       addq    $8, %rdi /* point %rdi at ptregs, fixed up for CR3 */
-       movq $-1,%rsi
        call do_nmi
+#ifdef CONFIG_KAISER
        /*
         * Unconditionally restore CR3.  We might be returning to
         * kernel code that needs user CR3, like just just before
         * a sysret.
         */
-#ifdef CONFIG_KAISER
        popq    %rax
        mov     %rax, %cr3
 #endif