• Stephen Smalley's avatar
    x86/mm: Warn on W^X mappings · e1a58320
    Stephen Smalley authored
    Warn on any residual W+X mappings after setting NX
    if DEBUG_WX is enabled.  Introduce a separate
    X86_PTDUMP_CORE config that enables the code for
    dumping the page tables without enabling the debugfs
    interface, so that DEBUG_WX can be enabled without
    exposing the debugfs interface.  Switch EFI_PGT_DUMP
    to using X86_PTDUMP_CORE so that it also does not require
    enabling the debugfs interface.
    
    On success it prints this to the kernel log:
    
      x86/mm: Checked W+X mappings: passed, no W+X pages found.
    
    On failure it prints a warning and a count of the failed pages:
    
      ------------[ cut here ]------------
      WARNING: CPU: 1 PID: 1 at arch/x86/mm/dump_pagetables.c:226 note_page+0x610/0x7b0()
      x86/mm: Found insecure W+X mapping at address ffffffff81755000/__stop___ex_table+0xfa8/0xabfa8
      [...]
      Call Trace:
       [<ffffffff81380a5f>] dump_stack+0x44/0x55
       [<ffffffff8109d3f2>] warn_slowpath_common+0x82/0xc0
       [<ffffffff8109d48c>] warn_slowpath_fmt+0x5c/0x80
       [<ffffffff8106cfc9>] ? note_page+0x5c9/0x7b0
       [<ffffffff8106d010>] note_page+0x610/0x7b0
       [<ffffffff8106d409>] ptdump_walk_pgd_level_core+0x259/0x3c0
       [<ffffffff8106d5a7>] ptdump_walk_pgd_level_checkwx+0x17/0x20
       [<ffffffff81063905>] mark_rodata_ro+0xf5/0x100
       [<ffffffff817415a0>] ? rest_init+0x80/0x80
       [<ffffffff817415bd>] kernel_init+0x1d/0xe0
       [<ffffffff8174cd1f>] ret_from_fork+0x3f/0x70
       [<ffffffff817415a0>] ? rest_init+0x80/0x80
      ---[ end trace a1f23a1e42a2ac76 ]---
      x86/mm: Checked W+X mappings: FAILED, 171 W+X pages found.
    Signed-off-by: default avatarStephen Smalley <sds@tycho.nsa.gov>
    Acked-by: default avatarKees Cook <keescook@chromium.org>
    Cc: Andy Lutomirski <luto@amacapital.net>
    Cc: Arjan van de Ven <arjan@linux.intel.com>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Brian Gerst <brgerst@gmail.com>
    Cc: Denys Vlasenko <dvlasenk@redhat.com>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Mike Galbraith <efault@gmx.de>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: linux-kernel@vger.kernel.org
    Link: http://lkml.kernel.org/r/1444064120-11450-1-git-send-email-sds@tycho.nsa.gov
    [ Improved the Kconfig help text and made the new option default-y
      if CONFIG_DEBUG_RODATA=y, because it already found buggy mappings,
      so we really want people to have this on by default. ]
    Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
    e1a58320
Kconfig.debug 12.1 KB