[PATCH v2] lkdtm: add bad USER_DS test
From: Kees Cook <hidden>
Date: 2017-03-31 16:35:31
Also in:
linux-s390, lkml
On Fri, Mar 24, 2017 at 10:51 AM, Kees Cook [off-list ref] wrote:
This adds CORRUPT_USER_DS to check that the get_fs() test on syscall return (via __VERIFY_PRE_USERMODE_STATE) still sees USER_DS. Since trying to deal with values other than USER_DS and KERNEL_DS across all architectures in a safe way is not sensible, this sets KERNEL_DS, but since that could be extremely dangerous if the protection is not present, it also raises SIGKILL for current, so that no matter what, the process will die. A successful test will be visible with a BUG(), like all the other LKDTM tests. Signed-off-by: Kees Cook <redacted>
Greg, can you add this to the drivers/misc tree when you get a moment? Thanks! -Kees
quoted hunk ↗ jump to hunk
--- drivers/misc/lkdtm.h | 1 + drivers/misc/lkdtm_bugs.c | 11 +++++++++++ drivers/misc/lkdtm_core.c | 1 + 3 files changed, 13 insertions(+)diff --git a/drivers/misc/lkdtm.h b/drivers/misc/lkdtm.h index 67d27be60405..3b4976396ec4 100644 --- a/drivers/misc/lkdtm.h +++ b/drivers/misc/lkdtm.h@@ -27,6 +27,7 @@ void lkdtm_REFCOUNT_ZERO_SUB(void); void lkdtm_REFCOUNT_ZERO_ADD(void); void lkdtm_CORRUPT_LIST_ADD(void); void lkdtm_CORRUPT_LIST_DEL(void); +void lkdtm_CORRUPT_USER_DS(void); /* lkdtm_heap.c */ void lkdtm_OVERWRITE_ALLOCATION(void);diff --git a/drivers/misc/lkdtm_bugs.c b/drivers/misc/lkdtm_bugs.c index e3f4cd8876b5..ed4f4c56c796 100644 --- a/drivers/misc/lkdtm_bugs.c +++ b/drivers/misc/lkdtm_bugs.c@@ -8,6 +8,8 @@ #include <linux/list.h> #include <linux/refcount.h> #include <linux/sched.h> +#include <linux/sched/signal.h> +#include <linux/uaccess.h> struct lkdtm_list { struct list_head node;@@ -279,3 +281,12 @@ void lkdtm_CORRUPT_LIST_DEL(void) else pr_err("list_del() corruption not detected!\n"); } + +void lkdtm_CORRUPT_USER_DS(void) +{ + pr_info("setting bad task size limit\n"); + set_fs(KERNEL_DS); + + /* Make sure we do not keep running with a KERNEL_DS! */ + force_sig(SIGKILL, current); +}diff --git a/drivers/misc/lkdtm_core.c b/drivers/misc/lkdtm_core.c index b9a4cd4a9b68..42d2b8e31e6b 100644 --- a/drivers/misc/lkdtm_core.c +++ b/drivers/misc/lkdtm_core.c@@ -199,6 +199,7 @@ struct crashtype crashtypes[] = { CRASHTYPE(OVERFLOW), CRASHTYPE(CORRUPT_LIST_ADD), CRASHTYPE(CORRUPT_LIST_DEL), + CRASHTYPE(CORRUPT_USER_DS), CRASHTYPE(CORRUPT_STACK), CRASHTYPE(UNALIGNED_LOAD_STORE_WRITE), CRASHTYPE(OVERWRITE_ALLOCATION), --2.7.4 -- Kees Cook Pixel Security
-- Kees Cook Pixel Security