mm: split ET_DYN ASLR from mmap ASLR

This fixes the "offset2lib" weakness in ASLR for arm, arm64, mips,
powerpc, and x86.  The problem is that if there is a leak of ASLR from
the executable (ET_DYN), it means a leak of shared library offset as
well (mmap), and vice versa.  Further details and a PoC of this attack
is available here:

  http://cybersecurity.upv.es/attacks/offset2lib/offset2lib.html

With this patch, a PIE linked executable (ET_DYN) has its own ASLR
region:

  $ ./show_mmaps_pie
  54859ccd6000-54859ccd7000 r-xp  ...  /tmp/show_mmaps_pie
  54859ced6000-54859ced7000 r--p  ...  /tmp/show_mmaps_pie
  54859ced7000-54859ced8000 rw-p  ...  /tmp/show_mmaps_pie
  7f75be764000-7f75be91f000 r-xp  ...  /lib/x86_64-linux-gnu/libc.so.6
  7f75be91f000-7f75beb1f000 ---p  ...  /lib/x86_64-linux-gnu/libc.so.6
  7f75beb1f000-7f75beb23000 r--p  ...  /lib/x86_64-linux-gnu/libc.so.6
  7f75beb23000-7f75beb25000 rw-p  ...  /lib/x86_64-linux-gnu/libc.so.6
  7f75beb25000-7f75beb2a000 rw-p  ...
  7f75beb2a000-7f75beb4d000 r-xp  ...  /lib64/ld-linux-x86-64.so.2
  7f75bed45000-7f75bed46000 rw-p  ...
  7f75bed46000-7f75bed47000 r-xp  ...
  7f75bed47000-7f75bed4c000 rw-p  ...
  7f75bed4c000-7f75bed4d000 r--p  ...  /lib64/ld-linux-x86-64.so.2
  7f75bed4d000-7f75bed4e000 rw-p  ...  /lib64/ld-linux-x86-64.so.2
  7f75bed4e000-7f75bed4f000 rw-p  ...
  7fffb3741000-7fffb3762000 rw-p  ...  [stack]
  7fffb377b000-7fffb377d000 r--p  ...  [vvar]
  7fffb377d000-7fffb377f000 r-xp  ...  [vdso]

The change is to add a call the newly created arch_mmap_rnd() into the
ELF loader for handling ET_DYN ASLR in a separate region from mmap ASLR,
as was already done on s390.  Removes CONFIG_BINFMT_ELF_RANDOMIZE_PIE,
which is no longer needed.

Signed-off-by: Kees Cook <[email protected]>
Reported-by: Hector Marco-Gisbert <[email protected]>
Cc: Russell King <[email protected]>
Reviewed-by: Ingo Molnar <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Ralf Baechle <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: "David A. Long" <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Arun Chandran <[email protected]>
Cc: Yann Droneaud <[email protected]>
Cc: Min-Hua Chen <[email protected]>
Cc: Paul Burton <[email protected]>
Cc: Alex Smith <[email protected]>
Cc: Markos Chandras <[email protected]>
Cc: Vineeth Vijayan <[email protected]>
Cc: Jeff Bailey <[email protected]>
Cc: Michael Holzheu <[email protected]>
Cc: Ben Hutchings <[email protected]>
Cc: Behan Webster <[email protected]>
Cc: Ismael Ripoll <[email protected]>
Cc: Jan-Simon Mller <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 0 insertions, 8 deletions

diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c
index 8c11536f972d..bb3367c5cb0b 100644
--- a/arch/s390/mm/mmap.c
+++ b/arch/s390/mm/mmap.c
@@ -177,14 +177,6 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
 	return addr;
 }
 
-unsigned long randomize_et_dyn(void)
-{
-	if (current->flags & PF_RANDOMIZE)
-		return arch_mmap_rnd();
-
-	return 0UL;
-}
-
 #ifndef CONFIG_64BIT
 
 /*