+ lkdtm-disable-kasan-for-rodatao.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: lkdtm: disable KASAN for rodata.o
has been added to the -mm tree.  Its filename is
     lkdtm-disable-kasan-for-rodatao.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/lkdtm-disable-kasan-for-rodatao.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/lkdtm-disable-kasan-for-rodatao.patch

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------------------------------------------------------
From: Marco Elver <elver@google.com>
Subject: lkdtm: disable KASAN for rodata.o

Building lkdtm with KASAN and Clang 11 or later results in the following
error when attempting to load the module:

  kernel tried to execute NX-protected page - exploit attempt? (uid: 0)
  BUG: unable to handle page fault for address: ffffffffc019cd70
  #PF: supervisor instruction fetch in kernel mode
  #PF: error_code(0x0011) - permissions violation
  ...
  RIP: 0010:asan.module_ctor+0x0/0xffffffffffffa290 [lkdtm]
  ...
  Call Trace:
   do_init_module+0x17c/0x570
   load_module+0xadee/0xd0b0
   __x64_sys_finit_module+0x16c/0x1a0
   do_syscall_64+0x34/0x50
   entry_SYSCALL_64_after_hwframe+0x44/0xa9

The reason is that rodata.o generates a dummy function that lives in
.rodata to validate that .rodata can't be executed; however, Clang 11 adds
KASAN globals support by generating module constructors to initialize
globals redzones.  When Clang 11 adds a module constructor to rodata.o, it
is also added to .rodata: any attempt to call it on initialization results
in the above error.

Therefore, disable KASAN instrumentation for rodata.o.

Link: https://lkml.kernel.org/r/20201214191413.3164796-1-elver@google.com
Signed-off-by: Marco Elver <elver@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/misc/lkdtm/Makefile |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/misc/lkdtm/Makefile~lkdtm-disable-kasan-for-rodatao
+++ a/drivers/misc/lkdtm/Makefile
@@ -11,6 +11,7 @@ lkdtm-$(CONFIG_LKDTM)		+= usercopy.o
 lkdtm-$(CONFIG_LKDTM)		+= stackleak.o
 lkdtm-$(CONFIG_LKDTM)		+= cfi.o
 
+KASAN_SANITIZE_rodata.o		:= n
 KASAN_SANITIZE_stackleak.o	:= n
 KCOV_INSTRUMENT_rodata.o	:= n
 
_

Patches currently in -mm which might be from elver@google.com are

lkdtm-disable-kasan-for-rodatao.patch
mm-add-kernel-electric-fence-infrastructure-fix.patch
mm-add-kernel-electric-fence-infrastructure-fix-2.patch
arm64-kfence-enable-kfence-for-arm64.patch
kfence-use-pt_regs-to-generate-stack-trace-on-faults.patch
kfence-documentation-add-kfence-documentation.patch
kfence-add-test-suite.patch
maintainers-add-entry-for-kfence.patch