x86/mm/pti: Make pti_clone_kernel_text() compile on 32 bit

CVE-2017-5754

The pti_clone_kernel_text() function references __end_rodata_hpage_align,
which is only present on x86-64.  This makes sense as the end of the rodata
section is not huge-page aligned on 32 bit.

Nevertheless a symbol is required for the function that points at the right
address for both 32 and 64 bit. Introduce __end_rodata_aligned for that
purpose and use it in pti_clone_kernel_text().

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Pavel Machek <pavel@ucw.cz>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: linux-mm@kvack.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eduardo Valentin <eduval@amazon.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: aliguori@amazon.com
Cc: daniel.gruss@iaik.tugraz.at
Cc: hughd@google.com
Cc: keescook@google.com
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Waiman Long <llong@redhat.com>
Cc: "David H . Gutteridge" <dhgutteridge@sympatico.ca>
Cc: joro@8bytes.org
Link: https://lkml.kernel.org/r/1531906876-13451-28-git-send-email-joro@8bytes.org
(cherry picked from commit 39d668e04edad25abe184fb329ce35a131146ee5)
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/arch/x86/include/asm/sections.h b/arch/x86/include/asm/sections.h
index 5c019d23d06b1168da0ea965d7c35bebd4d02307..4a911a382adedfdcd332b8b4884db6ff06e10533 100644 (file)
--- a/arch/x86/include/asm/sections.h
+++ b/arch/x86/include/asm/sections.h
@@ -7,6 +7,7 @@
 
 extern char __brk_base[], __brk_limit[];
 extern struct exception_table_entry __stop___ex_table[];
+extern char __end_rodata_aligned[];
 
 #if defined(CONFIG_X86_64)
 extern char __end_rodata_hpage_align[];

diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index b854ebf5851b7c8fb6225b53e7d3a81b16ec43db..71c3ccd95d927a613d836c395655d8ace3ab6789 100644 (file)
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -55,19 +55,22 @@ jiffies_64 = jiffies;
  * so we can enable protection checks as well as retain 2MB large page
  * mappings for kernel text.
  */
-#define X64_ALIGN_RODATA_BEGIN . = ALIGN(HPAGE_SIZE);
+#define X86_ALIGN_RODATA_BEGIN . = ALIGN(HPAGE_SIZE);
 
-#define X64_ALIGN_RODATA_END                                   \
+#define X86_ALIGN_RODATA_END                                   \
                . = ALIGN(HPAGE_SIZE);                          \
-               __end_rodata_hpage_align = .;
+               __end_rodata_hpage_align = .;                   \
+               __end_rodata_aligned = .;
 
 #define ALIGN_ENTRY_TEXT_BEGIN . = ALIGN(PMD_SIZE);
 #define ALIGN_ENTRY_TEXT_END   . = ALIGN(PMD_SIZE);
 
 #else
 
-#define X64_ALIGN_RODATA_BEGIN
-#define X64_ALIGN_RODATA_END
+#define X86_ALIGN_RODATA_BEGIN
+#define X86_ALIGN_RODATA_END                                   \
+               . = ALIGN(PAGE_SIZE);                           \
+               __end_rodata_aligned = .;
 
 #define ALIGN_ENTRY_TEXT_BEGIN
 #define ALIGN_ENTRY_TEXT_END
@@ -142,9 +145,9 @@ SECTIONS
 
        /* .text should occupy whole number of pages */
        . = ALIGN(PAGE_SIZE);
-       X64_ALIGN_RODATA_BEGIN
+       X86_ALIGN_RODATA_BEGIN
        RO_DATA(PAGE_SIZE)
-       X64_ALIGN_RODATA_END
+       X86_ALIGN_RODATA_END
 
        /* Data */
        .data : AT(ADDR(.data) - LOAD_OFFSET) {

diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index 035962ad3bba0da462b8748680172d012e27207a..fd1b094b613511c503039c8db393271209070af5 100644 (file)
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -471,7 +471,7 @@ void pti_clone_kernel_text(void)
         * clone the areas past rodata, they might contain secrets.
         */
        unsigned long start = PFN_ALIGN(_text);
-       unsigned long end = (unsigned long)__end_rodata_hpage_align;
+       unsigned long end = (unsigned long)__end_rodata_aligned;
 
        if (!pti_kernel_image_global_ok())
                return;