Commit-ID: 7cca071ccbd2a293ea69168ace6abbcdce53098e Gitweb: http://git.kernel.org/tip/7cca071ccbd2a293ea69168ace6abbcdce53098e Author: Kees Cook <[email protected]> AuthorDate: Wed, 17 Feb 2016 14:41:16 -0800 Committer: Ingo Molnar <[email protected]> CommitDate: Mon, 22 Feb 2016 08:51:38 +0100
lkdtm: Verify that '__ro_after_init' works correctly The new __ro_after_init section should be writable before init, but not after. Validate that it gets updated at init and can't be written to afterwards. Signed-off-by: Kees Cook <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Arnd Bergmann <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Brian Gerst <[email protected]> Cc: David Brown <[email protected]> Cc: Denys Vlasenko <[email protected]> Cc: Emese Revfy <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Mathias Krause <[email protected]> Cc: Michael Ellerman <[email protected]> Cc: PaX Team <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] Cc: linux-arch <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- drivers/misc/lkdtm.c | 29 ++++++++++++++++++++++++++--- 1 file changed, 26 insertions(+), 3 deletions(-) diff --git a/drivers/misc/lkdtm.c b/drivers/misc/lkdtm.c index 11fdadc..2a6eaf1 100644 --- a/drivers/misc/lkdtm.c +++ b/drivers/misc/lkdtm.c @@ -103,6 +103,7 @@ enum ctype { CT_EXEC_USERSPACE, CT_ACCESS_USERSPACE, CT_WRITE_RO, + CT_WRITE_RO_AFTER_INIT, CT_WRITE_KERN, }; @@ -140,6 +141,7 @@ static char* cp_type[] = { "EXEC_USERSPACE", "ACCESS_USERSPACE", "WRITE_RO", + "WRITE_RO_AFTER_INIT", "WRITE_KERN", }; @@ -162,6 +164,7 @@ static DEFINE_SPINLOCK(lock_me_up); static u8 data_area[EXEC_SIZE]; static const unsigned long rodata = 0xAA55AA55; +static unsigned long ro_after_init __ro_after_init = 0x55AA5500; module_param(recur_count, int, 0644); MODULE_PARM_DESC(recur_count, " Recursion level for the stack overflow test"); @@ -503,11 +506,28 @@ static void lkdtm_do_action(enum ctype which) break; } case CT_WRITE_RO: { - unsigned long *ptr; + /* Explicitly cast away "const" for the test. */ + unsigned long *ptr = (unsigned long *)&rodata; - ptr = (unsigned long *)&rodata; + pr_info("attempting bad rodata write at %p\n", ptr); + *ptr ^= 0xabcd1234; - pr_info("attempting bad write at %p\n", ptr); + break; + } + case CT_WRITE_RO_AFTER_INIT: { + unsigned long *ptr = &ro_after_init; + + /* + * Verify we were written to during init. Since an Oops + * is considered a "success", a failure is to just skip the + * real test. + */ + if ((*ptr & 0xAA) != 0xAA) { + pr_info("%p was NOT written during init!?\n", ptr); + break; + } + + pr_info("attempting bad ro_after_init write at %p\n", ptr); *ptr ^= 0xabcd1234; break; @@ -817,6 +837,9 @@ static int __init lkdtm_module_init(void) int n_debugfs_entries = 1; /* Assume only the direct entry */ int i; + /* Make sure we can write to __ro_after_init values during __init */ + ro_after_init |= 0xAA; + /* Register debugfs interface */ lkdtm_debugfs_root = debugfs_create_dir("provoke-crash", NULL); if (!lkdtm_debugfs_root) {
