From mboxrd@z Thu Jan 1 00:00:00 1970 From: Igor Stoppa Subject: [RFC PATCH v4 08/12] __wr_after_init: lkdtm test Date: Tue, 12 Feb 2019 01:27:45 +0200 Message-Id: <8708f8d2c541ce803072acec153f38011b271e90.1549927666.git.igor.stoppa@huawei.com> 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: Verify that trying to modify a variable with the __wr_after_init attribute will cause a crash. 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 --- drivers/misc/lkdtm/core.c | 3 +++ drivers/misc/lkdtm/lkdtm.h | 3 +++ drivers/misc/lkdtm/perms.c | 29 +++++++++++++++++++++++++++++ 3 files changed, 35 insertions(+) diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c index 2837dc77478e..73c34b17c433 100644 --- a/drivers/misc/lkdtm/core.c +++ b/drivers/misc/lkdtm/core.c @@ -155,6 +155,9 @@ static const struct crashtype crashtypes[] = { CRASHTYPE(ACCESS_USERSPACE), CRASHTYPE(WRITE_RO), CRASHTYPE(WRITE_RO_AFTER_INIT), +#ifdef CONFIG_PRMEM + CRASHTYPE(WRITE_WR_AFTER_INIT), +#endif CRASHTYPE(WRITE_KERN), CRASHTYPE(REFCOUNT_INC_OVERFLOW), CRASHTYPE(REFCOUNT_ADD_OVERFLOW), diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h index 3c6fd327e166..abba2f52ffa6 100644 --- a/drivers/misc/lkdtm/lkdtm.h +++ b/drivers/misc/lkdtm/lkdtm.h @@ -38,6 +38,9 @@ void lkdtm_READ_BUDDY_AFTER_FREE(void); void __init lkdtm_perms_init(void); void lkdtm_WRITE_RO(void); void lkdtm_WRITE_RO_AFTER_INIT(void); +#ifdef CONFIG_PRMEM +void lkdtm_WRITE_WR_AFTER_INIT(void); +#endif void lkdtm_WRITE_KERN(void); void lkdtm_EXEC_DATA(void); void lkdtm_EXEC_STACK(void); diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c index 53b85c9d16b8..f681730aa652 100644 --- a/drivers/misc/lkdtm/perms.c +++ b/drivers/misc/lkdtm/perms.c @@ -9,6 +9,7 @@ #include #include #include +#include #include /* Whether or not to fill the target memory area with do_nothing(). */ @@ -27,6 +28,10 @@ static const unsigned long rodata = 0xAA55AA55; /* This is marked __ro_after_init, so it should ultimately be .rodata. */ static unsigned long ro_after_init __ro_after_init = 0x55AA5500; +/* This is marked __wr_after_init, so it should be in .rodata. */ +static +unsigned long wr_after_init __wr_after_init = 0x55AA5500; + /* * This just returns to the caller. It is designed to be copied into * non-executable memory regions. @@ -104,6 +109,28 @@ void lkdtm_WRITE_RO_AFTER_INIT(void) *ptr ^= 0xabcd1234; } +#ifdef CONFIG_PRMEM + +void lkdtm_WRITE_WR_AFTER_INIT(void) +{ + unsigned long *ptr = &wr_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); + return; + } + + pr_info("attempting bad wr_after_init write at %p\n", ptr); + *ptr ^= 0xabcd1234; +} + +#endif + void lkdtm_WRITE_KERN(void) { size_t size; @@ -200,4 +227,6 @@ void __init lkdtm_perms_init(void) /* Make sure we can write to __ro_after_init values during __init */ ro_after_init |= 0xAA; + /* Make sure we can write to __wr_after_init during __init */ + wr_after_init |= 0xAA; } -- 2.19.1