From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Mon, 4 Dec 2017 15:07:14 +0100 Subject: [PATCH] x86/entry/gdt: Put per-CPU GDT remaps in ascending order MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit CVE-2017-5754 We currently have CPU 0's GDT at the top of the GDT range and higher-numbered CPUs at lower addresses. This happens because the fixmap is upside down (index 0 is the top of the fixmap). Flip it so that GDTs are in ascending order by virtual address. This will simplify a future patch that will generalize the GDT remap to contain multiple pages. Signed-off-by: Andy Lutomirski Signed-off-by: Thomas Gleixner Reviewed-by: Borislav Petkov Reviewed-by: Thomas Gleixner Cc: Boris Ostrovsky Cc: Borislav Petkov Cc: Borislav Petkov Cc: Brian Gerst Cc: Dave Hansen Cc: Dave Hansen Cc: David Laight Cc: Denys Vlasenko Cc: Eduardo Valentin Cc: Greg KH Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Juergen Gross Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Rik van Riel Cc: Will Deacon Cc: aliguori@amazon.com Cc: daniel.gruss@iaik.tugraz.at Cc: hughd@google.com Cc: keescook@google.com Link: https://lkml.kernel.org/r/20171204150605.471561421@linutronix.de Signed-off-by: Ingo Molnar (cherry picked from commit aaeed3aeb39c1ba69f0a49baec8cb728121d0a91) Signed-off-by: Andy Whitcroft Signed-off-by: Kleber Sacilotto de Souza (cherry picked from commit 9c37967fad2d6a525df53e0a40edcd652e5abaae) Signed-off-by: Fabian Grünbichler --- arch/x86/include/asm/desc.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/include/asm/desc.h b/arch/x86/include/asm/desc.h index f995e5a09136..22ee0a93b4f7 100644 --- a/arch/x86/include/asm/desc.h +++ b/arch/x86/include/asm/desc.h @@ -61,7 +61,7 @@ static inline struct desc_struct *get_current_gdt_rw(void) /* Get the fixmap index for a specific processor */ static inline unsigned int get_cpu_gdt_ro_index(int cpu) { - return FIX_GDT_REMAP_BEGIN + cpu; + return FIX_GDT_REMAP_END - cpu; } /* Provide the fixmap address of the remapped GDT */ -- 2.14.2