From mboxrd@z Thu Jan 1 00:00:00 1970 From: Igor Stoppa Subject: [RFC PATCH v5 10/12] __wr_after_init: rodata_test: test __wr_after_init Date: Thu, 14 Feb 2019 00:41:39 +0200 Message-Id: In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Cc: Igor Stoppa , Andy Lutomirski , Nadav Amit , Matthew Wilcox , Peter Zijlstra , Kees Cook , Dave Hansen , Mimi Zohar , Thiago Jung Bauermann , Ahmed Soliman , linux-integrity@vger.kernel.org, kernel-hardening@lists.openwall.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: The write protection of the __wr_after_init data can be verified with the same methodology used for const data. Signed-off-by: Igor Stoppa CC: Andy Lutomirski CC: Nadav Amit CC: Matthew Wilcox CC: Peter Zijlstra CC: Kees Cook CC: Dave Hansen CC: Mimi Zohar CC: Thiago Jung Bauermann CC: Ahmed Soliman CC: linux-integrity@vger.kernel.org CC: kernel-hardening@lists.openwall.com CC: linux-mm@kvack.org CC: linux-kernel@vger.kernel.org --- mm/rodata_test.c | 27 ++++++++++++++++++++++++--- 1 file changed, 24 insertions(+), 3 deletions(-) diff --git a/mm/rodata_test.c b/mm/rodata_test.c index e1349520b436..a669cf9f5a61 100644 --- a/mm/rodata_test.c +++ b/mm/rodata_test.c @@ -16,8 +16,23 @@ #define INIT_TEST_VAL 0xC3 +/* + * Note: __ro_after_init data is, for every practical effect, equivalent to + * const data, since they are even write protected at the same time; there + * is no need for separate testing. + * __wr_after_init data, otoh, is altered also after the write protection + * takes place and it cannot be exploitable for altering more permanent + * data. + */ + static const int rodata_test_data = INIT_TEST_VAL; +#ifdef CONFIG_PRMEM +static int wr_after_init_test_data __wr_after_init = INIT_TEST_VAL; +extern long __start_wr_after_init; +extern long __end_wr_after_init; +#endif + static bool test_data(char *data_type, const int *data, unsigned long start, unsigned long end) { @@ -59,7 +74,13 @@ static bool test_data(char *data_type, const int *data, void rodata_test(void) { - test_data("rodata", &rodata_test_data, - (unsigned long)&__start_rodata, - (unsigned long)&__end_rodata); + if (!test_data("rodata", &rodata_test_data, + (unsigned long)&__start_rodata, + (unsigned long)&__end_rodata)) + return; +#ifdef CONFIG_PRMEM + test_data("wr after init data", &wr_after_init_test_data, + (unsigned long)&__start_wr_after_init, + (unsigned long)&__end_wr_after_init); +#endif } -- 2.19.1