From e1a58320a38dfa72be48a0f1a3a92273663ba6db Mon Sep 17 00:00:00 2001 From: Stephen Smalley Date: Mon, 5 Oct 2015 12:55:20 -0400 Subject: 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: [] dump_stack+0x44/0x55 [] warn_slowpath_common+0x82/0xc0 [] warn_slowpath_fmt+0x5c/0x80 [] ? note_page+0x5c9/0x7b0 [] note_page+0x610/0x7b0 [] ptdump_walk_pgd_level_core+0x259/0x3c0 [] ptdump_walk_pgd_level_checkwx+0x17/0x20 [] mark_rodata_ro+0xf5/0x100 [] ? rest_init+0x80/0x80 [] kernel_init+0x1d/0xe0 [] ret_from_fork+0x3f/0x70 [] ? rest_init+0x80/0x80 ---[ end trace a1f23a1e42a2ac76 ]--- x86/mm: Checked W+X mappings: FAILED, 171 W+X pages found. Signed-off-by: Stephen Smalley Acked-by: Kees Cook Cc: Andy Lutomirski Cc: Arjan van de Ven Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner 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: Ingo Molnar --- arch/x86/include/asm/pgtable.h | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'arch/x86/include/asm/pgtable.h') diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index 59fc3414c68b..c0b41f111a9a 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -19,6 +19,13 @@ #include void ptdump_walk_pgd_level(struct seq_file *m, pgd_t *pgd); +void ptdump_walk_pgd_level_checkwx(void); + +#ifdef CONFIG_DEBUG_WX +#define debug_checkwx() ptdump_walk_pgd_level_checkwx() +#else +#define debug_checkwx() do { } while (0) +#endif /* * ZERO_PAGE is a global shared page that is always zero: used -- cgit v1.2.3