Messages in this thread Patch in this message | | | From | Kamal Mostafa <> | Subject | [PATCH 3.13.y-ckt 04/53] x86/nmi/64: Remove asm code that saves cr2 | Date | Thu, 6 Aug 2015 13:37:29 -0700 |
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3.13.11-ckt25 -stable review patch. If anyone has any objections, please let me know.
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From: Andy Lutomirski <luto@kernel.org>
commit 0e181bb58143cb4a2e8f01c281b0816cd0e4798e upstream.
Now that do_nmi saves cr2, we don't need to save it in asm.
This is a prerequisity for the fix for CVE-2015-3290.
Reviewed-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Borislav Petkov <bp@suse.de> Signed-off-by: Andy Lutomirski <luto@kernel.org> [bwh: Backported to 4.0: adjust filename, context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> Acked-by: John Johansen <john.johansen@canonical.com> Acked-by: Andy Whitcroft <apw@canonical.com> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> Signed-off-by: Andy Whitcroft <apw@canonical.com> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- arch/x86/kernel/entry_64.S | 18 ------------------ 1 file changed, 18 deletions(-)
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index ed0f923..2cd55a8 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -1919,29 +1919,11 @@ end_repeat_nmi: call save_paranoid DEFAULT_FRAME 0 - /* - * Save off the CR2 register. If we take a page fault in the NMI then - * it could corrupt the CR2 value. If the NMI preempts a page fault - * handler before it was able to read the CR2 register, and then the - * NMI itself takes a page fault, the page fault that was preempted - * will read the information from the NMI page fault and not the - * origin fault. Save it off and restore it if it changes. - * Use the r12 callee-saved register. - */ - movq %cr2, %r12 - /* paranoidentry do_nmi, 0; without TRACE_IRQS_OFF */ movq %rsp,%rdi movq $-1,%rsi call do_nmi - /* Did the NMI take a page fault? Restore cr2 if it did */ - movq %cr2, %rcx - cmpq %rcx, %r12 - je 1f - movq %r12, %cr2 -1: - testl %ebx,%ebx /* swapgs needed? */ jnz nmi_restore nmi_swapgs: -- 1.9.1
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