On Tue, Oct 06, 2015 at 02:54:53AM -0700, tip-bot for Stephen Smalley wrote:
> Commit-ID: e1a58320a38dfa72be48a0f1a3a92273663ba6db
> Gitweb: http://git.kernel.org/tip/e1a58320a38dfa72be48a0f1a3a92273663ba6db
> Author: Stephen Smalley <s...@tycho.nsa.gov>
> AuthorDate: Mon, 5 Oct 2015 12:55:20 -0400
> Committer: Ingo Molnar <mi...@kernel.org>
> CommitDate: Tue, 6 Oct 2015 11:11:48 +0200
>
> x86/mm: Warn on W^X mappings
>
> 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: Stephen Smalley <s...@tycho.nsa.gov>
> Acked-by: Kees Cook <keesc...@chromium.org>
> Cc: Andy Lutomirski <l...@amacapital.net>
> Cc: Arjan van de Ven <ar...@linux.intel.com>
> Cc: Borislav Petkov <b...@alien8.de>
> Cc: Brian Gerst <brge...@gmail.com>
> Cc: Denys Vlasenko <dvlas...@redhat.com>
> Cc: H. Peter Anvin <h...@zytor.com>
> Cc: Linus Torvalds <torva...@linux-foundation.org>
> Cc: Mike Galbraith <efa...@gmx.de>
> Cc: Peter Zijlstra <pet...@infradead.org>
> Cc: Thomas Gleixner <t...@linutronix.de>
> Cc: linux-kernel@vger.kernel.org
> Link:
> http://lkml.kernel.org/r/1444064120-11450-1-git-send-email-...@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: Ingo Molnar <mi...@kernel.org>
> ---
> arch/x86/Kconfig.debug | 36 +++++++++++++++++++++++++++++++++++-
> arch/x86/include/asm/pgtable.h | 7 +++++++
> arch/x86/mm/Makefile | 2 +-
> arch/x86/mm/dump_pagetables.c | 42
> +++++++++++++++++++++++++++++++++++++++++-
> arch/x86/mm/init_32.c | 2 ++
> arch/x86/mm/init_64.c | 2 ++
> 6 files changed, 88 insertions(+), 3 deletions(-)
...
> @@ -381,8 +398,26 @@ void ptdump_walk_pgd_level(struct seq_file *m, pgd_t
> *pgd)
> /* Flush out the last page */
> st.current_address = normalize_addr(PTRS_PER_PGD*PGD_LEVEL_MULT);
> note_page(m, &st, __pgprot(0), 0);
> + if (!checkwx)
> + return;
> + if (st.wx_pages)
> + pr_info("x86/mm: Checked W+X mappings: FAILED, %lu W+X pages
> found.\n",
> + st.wx_pages);
> + else
> + pr_info("x86/mm: Checked W+X mappings: passed, no W+X pages
> found.\n");
Do we really want to issue anything here in the success case? IMO, we
should be quiet if the check passes and only scream when something's
wrong...
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
--
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
